The influence of adherent surface preparation on bond durability

International Nuclear Information System (INIS)

Rider, A.N.; Arnott, D.R.; Olsson-Jacques, C.L.

1999-01-01

Full text: One of the major factors limiting the use of adhesive bonding is the problem associated with the production of adhesive joints that can maintain their initial strength over long periods of time in hostile environments. It is well known that the adherent surface preparation method is critical to the formation of a durable adhesive bond. Work presented in this paper focuses on the critical aspects of the surface preparation of aluminium employed for the manufacture of aluminium-epoxy joints. The surface preparation procedure examined is currently employed by the RAAF for repairs requiring metal to adhesive bonding. The influence of each step in the surface preparation on the ultimate bond durability performance of the adhesive joint is examined by a combination of methods. Double cantilever wedge style adhesive joints are loaded in mode 1 opening and then exposed to a humid environment. X-ray photoelectron spectroscopy (XPS) and contact angle measurements of the aluminium adherent before bonding provides information about the adherent surface chemistry. XPS is also employed to analyse the surfaces of the bonded specimens post failure to establish the locus of fracture. This approach provides important information regarding the properties influencing bond durability as well as the bond failure mechanisms. A two step bond degradation model was developed to qualitatively describe the observed bond durability performance and fracture data. The first step involves controlled moisture ingress by stress induced microporosity of the adhesive in the interfacial region. The second step determines the locus of fracture through the relative dominance of one of three competitive processes, viz: oxide degradation, polymer desorption, or polymer degradation. A key element of the model is the control exercised over the interfacial microporosity by the combined interaction of stress and the relative densities of strong and weak linkages at the metal to adhesive interface

Research on the Effects of Process Parameters on Surface Roughness in Wet-Activated Silicon Direct Bonding Base on Orthogonal Experiments

Directory of Open Access Journals (Sweden)

Lei NIE

2015-11-01

Full Text Available Surface roughness is a very important index in silicon direct bonding and it is affected by processing parameters in the wet-activated process. These parameters include the concentration of activation solution, holding time and treatment temperature. The effects of these parameters were investigated by means of orthogonal experiments. In order to analyze the wafer roughness more accurately, the bear ratio of the surface was used as the evaluation index. From the results of the experiments, it could be concluded that the concentration of the activation solution affected the roughness directly and the higher the concentration, the lower the roughness. Holding time did not affect the roughness as acutely as that of the concentration, but a reduced activation time decreased the roughness perceptibly. It was also discovered that the treatment temperature had a weak correlation with the surface roughness. Based on these conclusions, the parameters of concentration, temperature and holding time were optimized respectively as NH4OH:H2O2=1:1 (without water, 70 °C and 5 min. The results of bonding experiments proved the validity of the conclusions of orthogonal experiments.DOI: http://dx.doi.org/10.5755/j01.ms.21.4.9711

Cleaning of diffusion bonding surface by argon ion bombardment treatment

International Nuclear Information System (INIS)

Wang, Airu; Ohashi, Osamu; Yamaguchi, Norio; Aoki, Masanori; Higashi, Yasuo; Hitomi, Nobuteru

2003-01-01

The specimens of oxygen-free high conductivity copper, SUS304L stainless steel and pure iron were treated by argon ion bombardment and then were bonded by diffusion bonding method. The effects of argon ion bombardment treatment on faying surface morphology, tensile strength of bonding joints and inclusions at the fracture surface were investigated. The results showed that argon ion bombardment treatment was effective to remove the oxide film and contamination at the faying surface and improve the quality of joints. The tensile strength of the bonded joints was improved, and minimum bonding temperature to make the metallic bonding at the interface was lowered by argon ion bombardment treatment. At the joints with argon ion bombardment treatment, ductile fractured surface was seen and the amount of inclusions was obviously decreased

Fracture surface analysis in composite and titanium bonding: Part 1: Titanium bonding

Science.gov (United States)

Sanderson, K. A.; Wightman, J. P.

1985-01-01

Fractured lap shear Ti 6-4 adherends bonded with polyphenyquinoxaline (PPQ) and polysulfone were analyzed. The effects of adherend pretreatment, stress level, thermal aging, anodizing voltage, and modified adhesive of Ti 6-4 adherend bonded with PPQ on lap shear strength were studied. The effect of adherend pretreatment on lap shear strength was investigated for PS samples. Results of scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) used to study the surface topography and surface composition are also discussed.

Development of HIP bonding procedure and mechanical properties of HIP bonded joints for reduced activation ferritic steel F-82H

International Nuclear Information System (INIS)

Oda, Masahiro; Kurasawa, Toshimasa; Kuroda, Toshimasa; Hatano, Toshihisa; Takatsu, Hideyuki

1997-03-01

Structural materials of blanket components in fusion DEMO reactors will receive a neutron wall load more than 3-5MW/m 2 as well as exposed by surface heat flux more than 0.5MW/m 2 . A reduced activation ferritic steel F-82H has been developed by JAERI in collaboration with NKK from viewpoints of resistance for high temperature and neutron loads and lower radioactivity. This study intends to obtain basic performance of F-82H to establish the fabrication procedure of the first wall and blanket box by using Hot Isostatic Pressing (HIP) bonding. Before HIP bonding tests, effects of heat treatment temperature and surface roughness on mechanical properties of joints were investigated in the heat treatment tests and diffusion bonding tests, respectively. From these results, the optimum HIP bonding conditions and the post heat treatment were selected. Using these conditions, the HIP bonding tests were carried out to evaluate HIP bondability and to obtain mechanical properties of the joints. Sufficient HIP bonding performance was obtained under the temperature of 1040degC, the compressive stress of 150MPa, the holding time of 2h, and the surface roughness ∼μ m. Mechanical properties of HIP bonded joints with these conditions were similar to those of as-received base metal. An oxide formation on the surface to be bonded would need to be avoided for sufficient bonding. The bonding ratio, Charpy impact value and fatigue performance of the joints strongly depended on the HIP conditions, especially temperature, while micro-structure, Vickers hardness and tensile properties had little dependence on the HIP temperature. The surface roughness strongly affected the bonding ratio and would be required to be in the level of a few μ m. In the HIP bonding test of the welded material, the once-melted surface could be jointed by the HIP bonding under the above-mentioned procedure. (J.P.N.)

Influence of application method on surface free-energy and bond strength of universal adhesive systems to enamel.

Science.gov (United States)

Imai, Arisa; Takamizawa, Toshiki; Sai, Keiichi; Tsujimoto, Akimasa; Nojiri, Kie; Endo, Hajime; Barkmeier, Wayne W; Latta, Mark A; Miyazaki, Masashi

2017-10-01

The aim of the present study was to determine the influence of different adhesive application methods and etching modes on enamel bond effectiveness of universal adhesives using shear bond strength (SBS) testing and surface free-energy (SFE) measurements. The adhesives Scotchbond Universal, All-Bond Universal, Adhese Universal, and G-Premio Bond were used. Prepared bovine enamel specimens were divided into four groups, based on type of adhesive, and subjected to the following surface treatments: (i) total-etch mode with active application; (ii) total-etch mode with inactive application; (iii) self-etch mode with active application; and (iv) self-etch mode with inactive application. Bonded specimens were subjected to SBS testing. The SFE of the enamel surfaces with adhesive was measured after rinsing with acetone and water. The SBS values in total-etch mode were significantly higher than those in self-etch mode. In total-etch mode, significantly lower SBS values were observed with active application compared with inactive application; in contrast, in self-etch mode there were no significant differences in SBS between active and inactive applications. A reduction in total SFE was observed for active application compared with inactive application. The interaction between etching mode and application method was statistically significant, and the application method significantly affected enamel bond strength in total-etch mode. © 2017 Eur J Oral Sci.

Hydrogen-Bonding Surfaces for Ice Mitigation

Science.gov (United States)

Smith, Joseph G., Jr.; Wohl, Christopher J.; Kreeger, Richard E.; Hadley, Kevin R.; McDougall, Nicholas

2014-01-01

Ice formation on aircraft, either on the ground or in-flight, is a major safety issue. While ground icing events occur predominantly during the winter months, in-flight icing can happen anytime during the year. The latter is more problematic since it could result in increased drag and loss of lift. Under a Phase I ARMD NARI Seedling Activity, coated aluminum surfaces possessing hydrogen-bonding groups were under investigation for mitigating ice formation. Hydroxyl and methyl terminated dimethylethoxysilanes were prepared via known chemistries and characterized by spectroscopic methods. These materials were subsequently used to coat aluminum surfaces. Surface compositions were based on pure hydroxyl and methyl terminated species as well as mixtures of the two. Coated surfaces were characterized by contact angle goniometry. Receding water contact angle data suggested several potential surfaces that may exhibit reduced ice adhesion. Qualitative icing experiments performed under representative environmental temperatures using supercooled distilled water delivered via spray coating were inconclusive. Molecular modeling studies suggested that chain mobility affected the interface between ice and the surface more than terminal group chemical composition. Chain mobility resulted from the creation of "pockets" of increased free volume for longer chains to occupy.

Preservation of atomically clean silicon surfaces in air by contact bonding

DEFF Research Database (Denmark)

Grey, Francois; Ljungberg, Karin

1997-01-01

When two hydrogen-passivated silicon surfaces are placed in contact under cleanroom conditions, a weak bond is formed. Cleaving this bond under ultrahigh vacuum (UHV) conditions, and observing the surfaces with low energy electron diffraction and scanning tunneling microscopy, we find that the or...... reconstruction from oxidation in air, Contact bonding opens the way to novel applications of reconstructed semiconductor surfaces, by preserving their atomic structure intact outside of a UHV chamber. (C) 1997 American Institute of Physics.......When two hydrogen-passivated silicon surfaces are placed in contact under cleanroom conditions, a weak bond is formed. Cleaving this bond under ultrahigh vacuum (UHV) conditions, and observing the surfaces with low energy electron diffraction and scanning tunneling microscopy, we find...... that the ordered atomic structure of the surfaces is protected from oxidation, even after the bonded samples have been in air for weeks. Further, we show that silicon surfaces that have been cleaned and hydrogen-passivated in UHV can be contacted in UHV in a similarly hermetic fashion, protecting the surface...

Science and technology of plasma activated direct wafer bonding

Science.gov (United States)

Roberds, Brian Edward

This dissertation studied the kinetics of silicon direct wafer bonding with emphasis on low temperature bonding mechanisms. The project goals were to understand the topological requirements for initial bonding, develop a tensile test to measure the bond strength as a function of time and temperature and, using the kinetic information obtained, develop lower temperature methods of bonding. A reproducible surface metrology metric for bonding was best described by power spectral density derived from atomic force microscopy measurements. From the tensile strength kinetics study it was found that low annealing temperatures could be used to obtain strong bonds, but at the expense of longer annealing times. Three models were developed to describe the kinetics. A diffusion controlled model and a reaction rate controlled model were developed for the higher temperature regimes (T > 600sp°C), and an electric field assisted oxidation model was proposed for the low temperature range. An in situ oxygen plasma treatment was used to further enhance the field-controlled mechanism which resulted in dramatic increases in the low temperature bonding kinetics. Multiple internal transmission Fourier transform infrared spectroscopy (MIT-FTIR) was used to monitor species evolution at the bonded interface and a capacitance-voltage (CV) study was undertaken to investigate charge distribution and surface states resulting from plasma activation. A short, less than a minute, plasma exposure prior to contacting the wafers was found to obtain very strong bonds for hydrophobic silicon wafers at very low temperatures (100sp°C). This novel bonding method may enable new technologies involving heterogeneous material systems or bonding partially fabricated devices to become realities.

Correlation between catalytic activity and bonding and coordination number of atoms and molecules on transition metal surfaces: theory and experimental evidence

International Nuclear Information System (INIS)

Falicov, L.M.; Somorjai, G.A.

1985-01-01

Correlation between catalytic activity and low-energy local electronic fluctuation in transition metals is proposed. A theory and calculations are presented which indicate that maximum electronic fluctuants take place at high-coordination metal sites. Either (i) atomically rough surfaces that expose to the reactant molecules atoms with large numbers of nonmagnetic or weakly magnetic neighbors in the first or second layer at the surface or (ii) stepped and kinked surfaces are the most active in carrying out structure-sensitive catalytic reactions. The synthesis of ammonia from N 2 and H 2 over iron and rhenium surfaces, 1 H 2 / 2 H 2 exchange over stepped platinum crystal surfaces at low pressures, and the hydrogenolysis (C - C bond breaking) of isobutane at kinked platinum crystal surfaces are presented as experimental evidence in support of the theory

A simple surface treatment and characterization of AA 6061 aluminum alloy surface for adhesive bonding applications

International Nuclear Information System (INIS)

Saleema, N.; Sarkar, D.K.; Paynter, R.W.; Gallant, D.; Eskandarian, M.

2012-01-01

Highlights: ► A very simple surface treatment method to achieve excellent and durable aluminum adhesive bonding. ► Our method involves simple immersion of aluminum in very dilute NaOH solution at room temperature with no involvement of strong acids or multiple procedures. ► Surface analysis via various surface characterization techniques showed morphological and chemical modifications favorable for obtaining highly durable bond strengths on the treated surface. ► Safe, economical, reproducible and simple method, easily applicable in industries. - Abstract: Structural adhesive bonding of aluminum is widely used in aircraft and automotive industries. It has been widely noted that surface preparation of aluminum surfaces prior to adhesive bonding plays a significant role in improving the strength of the adhesive bond. Surface cleanliness, surface roughness, surface wettability and surface chemistry are controlled primarily by proper surface treatment methods. In this study, we have employed a very simple technique influencing all these criteria by simply immersing aluminum substrates in a very dilute solution of sodium hydroxide (NaOH) and we have studied the effect of varying the treatment period on the adhesive bonding characteristics. A bi-component epoxy adhesive was used to join the treated surfaces and the bond strengths were evaluated via single lap shear (SLS) tests in pristine as well as degraded conditions. Surface morphology, chemistry, crystalline nature and wettability of the NaOH treated surfaces were characterized using various surface analytical tools such as scanning electron microscopy and energy dispersive X-ray analysis (SEM/EDX), optical profilometry, infrared reflection absorption spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction and contact angle goniometry. Excellent adhesion characteristics with complete cohesive failure of the adhesive were encountered on the NaOH treated surfaces that are comparable to the benchmark

Novel fabrication method for 3D microstructures using surface-activated bonding and its application to micro-mechanical parts

Science.gov (United States)

Yamada, Takayuki; Takahashi, Mutsuya; Ozawa, Takashi; Tawara, Satoshi; Goto, Takayuki

2002-11-01

The purpose of this work is to demonstrate that a novel fabrication method for 3-D microstructures (FORMULA) is applicable to fabrication of micro mechanical parts with a large flexibility. This method is a kind of layer manufacturing method of thin films for metallic or dielectric microstructures using surface-activated bonding (SAB). The bonding interfaces of thin films are investigated by transmission electron microscope (TEM). Voids were observed at the interfaces of both pure aluminum films and Al-Cu alloy films. The ratio of void on the Al-Cu/Al-Cu interface is much larger than that of Al/Al interface, although the films have the same surface roughness of 3nm in Ra (average roughness). And approximately 10nm-thick amorphous intermediate layers were found at the interfaces. Furthermore, we have fabricated a micro gear of 900μm in diameter and 200μm in height, which is about ten times as large as our previous test pieces. Overhung structures such as a bridge structure and a cantilever were also fabricated without supporting layers beneath them.

Valence bond model potential energy surface for H4

International Nuclear Information System (INIS)

Silver, D.M.; Brown, N.J.

1980-01-01

Potential energy surfaces for the H 4 system are derived using the valence bond procedure. An ab initio evaluation of the valence bond energy expression is described and some of its numerical properties are given. Next, four semiempirical evaluations of the valence bond energy are defined and parametrized to yield reasonable agreement with various ab initio calculations of H 4 energies. Characteristics of these four H 4 surfaces are described by means of tabulated energy minima and equipotential contour maps for selected geometrical arrangements of the four nuclei

Effect of surface treatment of FRC-Post on bonding strength to resin cements

Directory of Open Access Journals (Sweden)

Chan-Hyun Park,

2011-03-01

Full Text Available Objectives The purpose of this study was to evaluate the effect of surface treatment of FRC-Post on bonding strength to resin cements. Materials and Methods Pre-surface treated LuxaPost (DMG, Rely-X Fiber Post (3M ESPE and self adhesive resin cement Rely-X Unicem (3M ESPE, conventional resin cement Rely-X ARC (3M ESPE, and Rely-X Ceramic Primer (3M ESPE were used. After completing the surface treatments of the posts, posts and resin cement were placed in clear molds and photo-activation was performed. The specimens were sectioned perpendicular to the FRC-Post into 2 mm-thick segments, and push-out strength were measured. The results of bond strength value were statistically analyzed using independent samples t-test and one-way ANOVA with multiple comparisons using Scheffe's test. Results Silanization of posts affect to the bond strength in LuxaPost, and did not affect in Rely-X Fiber Post. Rely-X ARC showed higher value than Rely-X Unicem. Conclusions Silanization is needed to enhance the bond strength between LuxaPost and resin cements.

The Effect of Artificial Aging on The Bond Strength of Heat-activated Acrylic Resin to Surface-treated Nickel-chromium-beryllium Alloy.

Science.gov (United States)

Al Jabbari, Youssef S; Zinelis, Spiros; Al Taweel, Sara M; Nagy, William W

2016-01-01

The debonding load of heat-activated polymethylmethacrylate (PMMA) denture base resin material to a nickel-chromium-beryllium (Ni-Cr-Be) alloy conditioned by three different surface treatments and utilizing two different commercial bonding systems was investigated. Denture resin (Lucitone-199) was bonded to Ni-Cr-Be alloy specimens treated with Metal Primer II, the Rocatec system with opaquer and the Rocatec system without opaquer. Denture base resin specimens bonded to non-treated sandblasted Ni-Cr-Be alloy were used as controls. Twenty samples for each treatment condition (80 specimens) were tested. The 80 specimens were divided into two categories, thermocycled and non-thermocycled, containing four groups of ten specimens each. The non-thermocycled specimens were tested after 48 hours' storage in room temperature water. The thermocycled specimens were tested after 2,000 cycles in 4°C and 55°C water baths. The debonding load was calculated in Newtons (N), and collected data were subjected by non parametric test Kruskal-Wallis One Way Analysis of Variance on Ranks and Dunn's post hoc test at the α = 0.05. The Metal Primer II and Rocatec system without opaquer groups produced significantly higher bond strengths (119.9 and 67.6 N), respectively, than did the sandblasted and Rocatec system with opaquer groups, where the bond strengths were 2.6 N and 0 N, respectively. The Metal Primer II was significantly different from all other groups (P<0.05). The bond strengths of all groups were significantly decreased (P<0.05) after thermocycling. Although thermocycling had a detrimental effect on the debonding load of all surface treatments tested, the Metal Primer II system provided higher values among all bonding systems tested, before and after thermocycling.

Tantalum surface oxidation: Bond relaxation, energy entrapment, and electron polarization

Energy Technology Data Exchange (ETDEWEB)

Guo, Yongling [Key Laboratory of Low-Dimensional Materials and Application Technologies (Ministry of Education), Hunan Provincial Key Laboratory of Thin Film Materials and Devices, Faculty of Materials Science and Engineering, Xiangtan University, Hunan 411105 (China); Bo, Maolin [Yangtze Normal University, College of Mechanical and Electrical Engineering, Chongqing 408100 (China); Wang, Yan [School of Information and Electronic Engineering, Hunan University of Science and Technology, Hunan 411201 (China); Liu, Yonghui [Key Laboratory of Low-Dimensional Materials and Application Technologies (Ministry of Education), Hunan Provincial Key Laboratory of Thin Film Materials and Devices, Faculty of Materials Science and Engineering, Xiangtan University, Hunan 411105 (China); Sun, Chang Q. [NOVITAS, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Huang, Yongli, E-mail: huangyongli@xtu.edu.cn [Key Laboratory of Low-Dimensional Materials and Application Technologies (Ministry of Education), Hunan Provincial Key Laboratory of Thin Film Materials and Devices, Faculty of Materials Science and Engineering, Xiangtan University, Hunan 411105 (China)

2017-02-28

Graphical abstract: The bond, electron and energy relaxation result in core level energy shift, local densification, quantum entrapment and electron polarization of bonding electrons. - Highlights: • Increasing the oxygen coverage lowers the adsorption energy associated with lattice reconstruction. • Electrons transfer from Ta surface atoms to sp-hydrated oxygen, creating dipole moment that decreases the work function. • Oxygen chemisorption modified valence density-of-state (DOS) for Ta with four excessive DOS features: O−Ta bonding, O{sup 2−} lone pairs, Ta+ electron holes, and the lone-pair polarized Ta dipoles. • The bond, electron and energy relaxation between surface undercoordinated atoms are responsible for core level energy shift, local densification, quantum entrapment and electron polarization of bonding electrons. - Abstract: A combination of photoelectron spectrometric analysis and density functional theory calculations has enabled reconciliation of the bond-energy-electron relaxation for the Ta(100, 110, 111) surfaces chemisorbed with oxygen at different coverages. Results show that increasing oxygen coverage lowers the adsorption energy associated with lattice reconstruction. Valence electrons transfer from Ta surface atoms to oxygen to create four excessive DOS features in terms of O−Ta bonding, lone pairs of oxygen, Ta{sup +} electron holes, and polarized Ta dipoles. Oxidation proceeds in the following dynamics: oxygen gets electrons from two neighboring Ta atoms left behind Ta{sup +}; the sp{sup 3}-orbital hybridization takes place with additional two electron lone pairs, the lone pairs polarize the other two Ta neighbors becoming dipoles. X-ray photoelectron spectral analysis results in the 4f binding energy of an isolated Ta atom and its shift upon bond formation and oxidation. Exercises provide not only a promising numerical approach for the quantitative information about the bond and electronic behavior but also consistent

Tantalum surface oxidation: Bond relaxation, energy entrapment, and electron polarization

International Nuclear Information System (INIS)

Guo, Yongling; Bo, Maolin; Wang, Yan; Liu, Yonghui; Sun, Chang Q.; Huang, Yongli

2017-01-01

Graphical abstract: The bond, electron and energy relaxation result in core level energy shift, local densification, quantum entrapment and electron polarization of bonding electrons. - Highlights: • Increasing the oxygen coverage lowers the adsorption energy associated with lattice reconstruction. • Electrons transfer from Ta surface atoms to sp-hydrated oxygen, creating dipole moment that decreases the work function. • Oxygen chemisorption modified valence density-of-state (DOS) for Ta with four excessive DOS features: O−Ta bonding, O"2"− lone pairs, Ta+ electron holes, and the lone-pair polarized Ta dipoles. • The bond, electron and energy relaxation between surface undercoordinated atoms are responsible for core level energy shift, local densification, quantum entrapment and electron polarization of bonding electrons. - Abstract: A combination of photoelectron spectrometric analysis and density functional theory calculations has enabled reconciliation of the bond-energy-electron relaxation for the Ta(100, 110, 111) surfaces chemisorbed with oxygen at different coverages. Results show that increasing oxygen coverage lowers the adsorption energy associated with lattice reconstruction. Valence electrons transfer from Ta surface atoms to oxygen to create four excessive DOS features in terms of O−Ta bonding, lone pairs of oxygen, Ta"+ electron holes, and polarized Ta dipoles. Oxidation proceeds in the following dynamics: oxygen gets electrons from two neighboring Ta atoms left behind Ta"+; the sp"3-orbital hybridization takes place with additional two electron lone pairs, the lone pairs polarize the other two Ta neighbors becoming dipoles. X-ray photoelectron spectral analysis results in the 4f binding energy of an isolated Ta atom and its shift upon bond formation and oxidation. Exercises provide not only a promising numerical approach for the quantitative information about the bond and electronic behavior but also consistent insight into the

Strength and leak testing of plasma activated bonded interfaces

DEFF Research Database (Denmark)

Visser, M.M.; Weichel, Steen; Reus, Roger De

2002-01-01

on detection of changes in membrane deflections. The detection limit for leak was 8E-13 mbar l/s. For comparison, strength and leak tests were also performed with regular fusion bonded wafers annealed at 1100 degreesC. The PAB was found to withstand post-processing steps such as RCA cleaning, 24 h in de......-ionised water (DIW), 24 h in 2.5% HF, 24 h in acetone and 60 s in a resist developer. By analysing the thin silicon oxide present on the surfaces to be bonded with optical methods, the influence of pre-cleaning and activation process parameters was investigated....

New Concept of C–H and C–C Bond Activation via Surface Organometallic Chemistry

KAUST Repository

Samantaray, Manoja; Dey, Raju; Kavitake, Santosh Giridhar; Basset, Jean-Marie

2015-01-01

In this chapter we describe the recent applications of well-defined oxidesupported metal alkyls/alkylidenes/alkylidynes and hydrides of group IV, V, and VI transition metals in the field of C–H and C–C bond activation. The activation of ubiquitous C

Influence of various surface-conditioning methods on the bond strength of metal brackets to ceramic surfaces

NARCIS (Netherlands)

Schmage, P; Nergiz, [No Value; Herrmann, W; Ozcan, M; Nergiz, Ibrahim; �zcan, Mutlu

With the increase in adult orthodontic treatment comes the need to find a reliable method for bonding orthodontic brackets onto metal or ceramic crowns and fixed partial dentures. In this study, shear bond strength and surface roughness tests were used to examine the effect of 4 different surface

Tensile Bond Strength of Self Adhesive Resin Cement After Various Surface Treatment of Enamel.

Science.gov (United States)

Sekhri, Sahil; Mittal, Sanjeev; Garg, Sandeep

2016-01-01

In self adhesive resin cements adhesion is achieved to dental surface without surface pre-treatment, and requires only single step application. This makes the luting procedure less technique-sensitive and decreases postoperative sensitivity. The purpose of this study was to evaluate bond strength of self adhesive resin after surface treatment of enamel for bonding base metal alloy. On the labial surface of 64 central incisor rectangular base metal block of dimension 6 mm length, 5mm width and 1 mm height was cemented with RelyX U200 and Maxcem Elite self adhesive cements with and without surface treatment of enamel. Surface treatment of enamel was application of etchant, one step bonding agent and both. Tensile bond strength of specimen was measured with universal testing machine at a cross head speed of 1mm/min. Least tensile bond strength (MPa) was in control group i.e. 1.33 (0.32) & 1.59 (0.299), Highest bond strength observed when enamel treated with both etchant and bonding agent i.e. 2.72 (0.43) & 2.97 (0.19) for Relyx U200 and Elite cement. When alone etchant and bonding agent were applied alone bond strength is 2.19 (0.18) & 2.24 (0.47) for Relyx U200, and 2.38 (0.27) 2.49 (0.16) for Max-cem elite. Mean bond strength was higher in case of Max-cem Elite as compared to RelyX U200 resin cement, although differences were non-significant (p > 0.05). Surface treatment of enamel increases the bond strength of self adhesive resin cement.

Factors affecting the shear bond strength of metal and ceramic brackets bonded to different ceramic surfaces.

Science.gov (United States)

Abu Alhaija, Elham S J; Abu AlReesh, Issam A; AlWahadni, Ahed M S

2010-06-01

The aims of this study were to evaluate the shear bond strength (SBS) of metal and ceramic brackets bonded to two different all-ceramic crowns, IPS Empress 2 and In-Ceram Alumina, to compare the SBS between hydrofluoric acid (HFA), phosphoric acid etched, and sandblasted, non-etched all-ceramic surfaces. Ninety-six all-ceramic crowns were fabricated resembling a maxillary left first premolar. The crowns were divided into eight groups: (1) metal brackets bonded to sandblasted 9.6 per cent HFA-etched IPS Empress 2 crowns; (2) metal brackets bonded to sandblasted 9.6 per cent HFA-etched In-Ceram crowns; (3) ceramic brackets bonded to sandblasted 9.6 per cent HFA-etched IPS Empress 2 crowns; (4) ceramic brackets bonded to sandblasted 9.6 per cent HFA-etched In-Ceram crowns; (5) metal brackets bonded to sandblasted 37 per cent phosphoric acid-etched IPS Empress 2 crowns; (6) metal brackets bonded to sandblasted 37 per cent phosphoric acid-etched In-Ceram crowns; (7) metal brackets bonded to sandblasted, non-etched IPS Empress 2 crowns; and (8) metal brackets bonded to sandblasted, non-etched In-Ceram crowns. Metal and ceramic orthodontic brackets were bonded using a conventional light polymerizing adhesive resin. An Instron universal testing machine was used to determine the SBS at a crosshead speed of 0.1 mm/minute. Comparison between groups was performed using a univariate general linear model and chi-squared tests. The highest mean SBS was found in group 3 (120.15 +/- 45.05 N) and the lowest in group 8 (57.86 +/- 26.20 N). Of all the variables studied, surface treatment was the only factor that significantly affected SBS (P Empress 2 and In-Ceram groups.

Tensile Bond Strength of Self Adhesive Resin Cement After Various Surface Treatment of Enamel

Science.gov (United States)

Sekhri, Sahil; Garg, Sandeep

2016-01-01

Introduction In self adhesive resin cements adhesion is achieved to dental surface without surface pre-treatment, and requires only single step application. This makes the luting procedure less technique-sensitive and decreases postoperative sensitivity. Aim The purpose of this study was to evaluate bond strength of self adhesive resin after surface treatment of enamel for bonding base metal alloy. Materials and Methods On the labial surface of 64 central incisor rectangular base metal block of dimension 6 mm length, 5mm width and 1 mm height was cemented with RelyX U200 and Maxcem Elite self adhesive cements with and without surface treatment of enamel. Surface treatment of enamel was application of etchant, one step bonding agent and both. Tensile bond strength of specimen was measured with universal testing machine at a cross head speed of 1mm/min. Results Least tensile bond strength (MPa) was in control group i.e. 1.33 (0.32) & 1.59 (0.299), Highest bond strength observed when enamel treated with both etchant and bonding agent i.e. 2.72 (0.43) & 2.97 (0.19) for Relyx U200 and Elite cement. When alone etchant and bonding agent were applied alone bond strength is 2.19 (0.18) & 2.24 (0.47) for Relyx U200, and 2.38 (0.27) 2.49 (0.16) for Max-cem elite. Mean bond strength was higher in case of Max-cem Elite as compared to RelyX U200 resin cement, although differences were non–significant (p > 0.05). Conclusion Surface treatment of enamel increases the bond strength of self adhesive resin cement. PMID:26894165

Surface modification for bonding between amalgam and orthodontic brackets.

Science.gov (United States)

Wongsamut, Wittawat; Satrawaha, Sirichom; Wayakanon, Kornchanok

2017-01-01

Testing of methods to enhance the shear bond strength (SBS) between orthodontic metal brackets and amalgam by sandblasting and different primers. Three hundred samples of amalgam restorations (KerrAlloy ® ) were prepared in self-cured acrylic blocks, polished, and divided into two groups: nonsandblasted and sandblasted. Each group was divided into five subgroups with different primers used in surface treatment methods, with a control group of bonded brackets on human mandibular incisors. Following the surface treatments, mandibular incisor brackets (Unitek ® ) were bonded on the amalgam with adhesive resin (Transbond XT ® ). The SBS of the samples was tested. The adhesive remnant index (ARI) and failure modes were then determined under a stereo-microscope. Two-way analysis of variance, Chi-square, and Kruskal-Wallis tests were performed to calculate the correlations between and among the SBS and ARI values, the failure modes, and surface roughness results. There were statistically significant differences of SBS among the different adhesive primers and sandblasting methods ( P 0.05). Using adhesive primers with sandblasting together effectively enhances the SBS between orthodontic metal brackets and amalgam. The two primers with the ingredient methacryloxydecyl dihydrogen phosphate (MDP) monomer, Alloy Primer ® and Assure Plus ® , were the most effective. Including sandblasting in the treatment is essential to achieve the bonding strength required.

Amalgam shear bond strength to dentin using different bonding agents.

Science.gov (United States)

Vargas, M A; Denehy, G E; Ratananakin, T

1994-01-01

This study evaluated the shear bond strength of amalgam to dentin using five different bonding agents: Amalgambond Plus, Optibond, Imperva Dual, All-Bond 2, and Clearfil Liner Bond. Flat dentin surfaces obtained by grinding the occlusal portion of 50 human third molars were used for this study. To contain the amalgam on the tooth surface, cylindrical plastic molds were placed on the dentin and secured with sticky wax. The bonding agents were then applied according to the manufacturers' instructions or light activated and Tytin amalgam was condensed into the plastic molds. The samples were thermocycled and shear bond strengths were determined using an Instron Universal Testing Machine. Analysis by one-way ANOVA indicated significant difference between the five groups (P < 0.05). The bond strength of amalgam to dentin was significantly higher with Amalgambond Plus using the High-Performance Additive than with the other four bonding agents.

Surface chemistry and bonding configuration of ultrananocrystalline diamond surfaces and their effects on nanotribological properties

International Nuclear Information System (INIS)

Sumant, A. V.; Grierson, D. S.; Carpick, R. W.; Gerbi, J. E.; Carlisle, J. A.; Auciello, O.

2007-01-01

We present a comprehensive study of surface composition and nanotribology for ultrananocrystalline diamond (UNCD) surfaces, including the influence of film nucleation on these properties. We describe a methodology to characterize the underside of the films as revealed by sacrificial etching of the underlying substrate. This enables the study of the morphology and composition resulting from the nucleation and initial growth of the films, as well as the characterization of nanotribological properties which are relevant for applications including micro-/nanoelectromechanical systems. We study the surface chemistry, bonding configuration, and nanotribological properties of both the topside and the underside of the film with synchrotron-based x-ray absorption near-edge structure spectroscopy to identify the bonding state of the carbon atoms, x-ray photoelectron spectroscopy to determine the surface chemical composition, Auger electron spectroscopy to further verify the composition and bonding configuration, and quantitative atomic force microscopy to study the nanoscale topography and nanotribological properties. The films were grown on SiO 2 after mechanically polishing the surface with detonation synthesized nanodiamond powder, followed by ultrasonication in a methanol solution containing additional nanodiamond powder. The sp 2 fraction, morphology, and chemistry of the as-etched underside are distinct from the topside, exhibiting a higher sp 2 fraction, some oxidized carbon, and a smoother morphology. The nanoscale single-asperity work of adhesion between a diamond nanotip and the as-etched UNCD underside is far lower than for a silicon-silicon interface (59.2±2 vs 826±186 mJ/m 2 , respectively). Exposure to atomic hydrogen dramatically reduces nanoscale adhesion to 10.2±0.4 mJ/m 2 , at the level of van der Waals' interactions and consistent with recent ab initio calculations. Friction is substantially reduced as well, demonstrating a direct link between the

Real-Time Observation of Surface Bond Breaking with an X-ray Laser

DEFF Research Database (Denmark)

Dell'Angela, M.; Anniyev, T.; Beye, M.

2013-01-01

molecules interact weakly with the surface but translate along it and exchange energy without forming localized surface bonds. Dell'Angela et al. (p. 1302) found evidence for such a state in changes in x-ray absorption and emission spectra of CO molecules adsorbed on a ruthenium surface after optical...... and that are bonded less strongly than the chemisorbed state....

Shear bond strength of two bonding systems on dentin surfaces prepared with Er:YAG laser

International Nuclear Information System (INIS)

Dall'Magro, Eduardo

2001-01-01

The purpose of this study was to examine the shear bond strength of two bonding dentin systems, one 'one step' (Single Bond - 3M) and one 'self-etching' (Prompt-L-ESPE), when applied on dentin surfaces prepared with Er:YAG laser (2,94μm) that underwent ar not, acid etched. Forty one human molars just extracted were selected and after the cut with diamond disc and included in acrylic resin, resulting in 81 specimens (hemi crowns). After, the specimens were divided in one group treated with sand paper and another two groups treated with Er:YAG laser with 200 mJ and 250 mJ of energy and 2 Hz of frequency. Next, the prepared surfaces received three treatments with following application: 1) acid + Single Bond + Z 250 resin, 2) prompt-L-Pop + Z 250 resin, and 3) acid without, Single Bond + Z 250 resin. The Z 250 resin was applied and photopolymerized in increments on a Teflon matrix that belonged to an apparatus called 'Assembly Apparatus' machine producing cylinders of 3,5 mm of diameter and 5 mm of height. After these specimens were submitted to thermo cycling during 1 minute the 55 deg C and during 1 minute with 5 deg C with a total of 500 cycles for specimen, and the measures of shear bond strength were abstained using EMIC model DL 2000 rehearsed machine, with speed of 0,5 mm/min, measuring the final rupture tension (Mpa). The results showed an statistic superiority of 5% of probability level in dentin flattened with sandpaper and with laser using 200 mJ of energy with aspect to the ones flattened with laser using 250 mJ of energy. It was observed that using 'Single Bond' bonding dentin system the marks were statistically superior at 5% of probability with reference to the use of the Prompt-L-Pop adhesive system. So, it was concluded that Er:YAG Laser with 200 mJ of energy produced similar dentin cavity prepare than sandpaper and Single Bond seemed the best bonding agent system between restorative material and dentin. (author)

Effects of surface treatment of provisional crowns on the shear bond strength of brackets

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Josiane Xavier de Almeida

2013-08-01

Full Text Available OBJECTIVE: To assess the adhesive resistance of metallic brackets bonded to temporary crowns made of acrylic resin after different surface treatments. METHODS: 180 specimens were made of Duralay and randomly divided into 6 groups (n = 30 according to surface treatment and bonding material: G1 - surface roughening with Soflex and bonding with Duralay; G2 - roughening with aluminum oxide blasting and bonding with Duralay; G3 - application of monomer and bonding with Duralay; G4 - roughening with Soflex and bonding with Transbond XT; G5 - roughening with aluminum oxide blasting and bonding with Transbond XT and G6: application of monomer and bonding with Transbond. The results were statistically assessed by ANOVA/Games-Howell. RESULTS: The means (MPa were: G1= 18.04, G2= 22.64, G3= 22.4, G4= 9.71, G5= 11.23, G6= 9.67. The Adhesive Remnant Index (ARI ranged between 2 and 3 on G1, G2 and G3 whereas in G4, G5 and G6 it ranged from 0 to 1, showing that only the material affects the pattern of adhesive flaw. CONCLUSION: The surface treatment and the material influenced adhesive resistance of brackets bonded to temporary crowns. Roughening by aluminum blasting increased bond strength when compared to Soflex, in the group bonded with Duralay. The bond strength of Duralay acrylic resin was superior to that of Transbond XT composite resin.

Effects of surface treatment on bond strength between dental resin agent and zirconia ceramic

Energy Technology Data Exchange (ETDEWEB)

Moradabadi, Ashkan [Department of Electrochemistry, Universität Ulm, Ulm (Germany); Roudsari, Sareh Esmaeily Sabet [Department of Optoelectonics, Universität Ulm, Ulm (Germany); Yekta, Bijan Eftekhari [School of Materials Engineering, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Rahbar, Nima, E-mail: nrahbar@wpi.edu [Department of Civil and Environmental Engineering, Worcester Polytechnic Institute, Worcester, MA 01609 (United States)

2014-01-01

This paper presents the results of an experimental study to understand the dominant mechanism in bond strength between dental resin agent and zirconia ceramic by investigating the effects of different surface treatments. Effects of two major mechanisms of chemical and micromechanical adhesion were evaluated on bond strength of zirconia to luting agent. Specimens of yttrium-oxide-partially-stabilized zirconia blocks were fabricated. Seven groups of specimens with different surface treatment were prepared. 1) zirconia specimens after airborne particle abrasion (SZ), 2) zirconia specimens after etching (ZH), 3) zirconia specimens after airborne particle abrasion and simultaneous etching (HSZ), 4) zirconia specimens coated with a layer of a Fluorapatite-Leucite glaze (GZ), 5) GZ specimens with additional acid etching (HGZ), 6) zirconia specimens coated with a layer of salt glaze (SGZ) and 7) SGZ specimens after etching with 2% HCl (HSGZ). Composite cylinders were bonded to airborne-particle-abraded surfaces of ZirkonZahn specimens with Panavia F2 resin luting agent. Failure modes were examined under 30 × magnification and the effect of surface treatments was analyzed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). SZ and HSZ groups had the highest and GZ and SGZ groups had the lowest mean shear bond strengths among all groups. Mean shear bond strengths were significantly decreased by applying a glaze layer on zirconia surfaces in GZ and SGZ groups. However, bond strengths were improved after etching process. Airborne particle abrasion resulted in higher shear bond strengths compared to etching treatment. Modes of failure varied among different groups. Finally, it is concluded that micromechanical adhesion was a more effective mechanism than chemical adhesion and airborne particle abrasion significantly increased mean shear bond strengths compared with another surface treatments. - Highlights: • Understanding the dominant mechanism of bonding

Effect of different surface treatments on bond strength, surface and microscopic structure of zirconia ceramic

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Zeinab R. El-Shrkawy

2016-06-01

Conclusions: (1 Surface treatments of Y-TZP ceramic together with MDP primer and silane-coupling agent application improve the bond strength to resin cement. (2 Plasma-Silica coating and plasma-oxygen treatment, both are valuable methods that improve the bond strength of resin cement to Y-TZP ceramic. (3 Silica coating by plasma technology provides durable bond strength and can be a promising alternative pretreatment before silane application to enhance bonding with zirconia ceramic. (4 Tetragonal-monoclinic phase transformation had occurred in Y-TZP samples received both types of plasma treatment.

Real earnings management activities prior to bond issuance

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Cristhian Mellado-Cid

2017-07-01

Full Text Available We examine real activities manipulation by firms prior to their debt issuances and how such manipulation activities affect bond yield spreads. We find that bond-issuing firms increase their real activities manipulation in the five quarters leading to a bond issuance. We document an inverse association between yield spread and pre-issue real activities manipulation, i.e., firms engaged in abnormally high levels of real activities manipulation are associated with subsequent lower cost of debt.

Relationship between enamel bond fatigue durability and surface free-energy characteristics with universal adhesives.

Science.gov (United States)

Nagura, Yuko; Tsujimoto, Akimasa; Barkmeier, Wayne W; Watanabe, Hidehiko; Johnson, William W; Takamizawa, Toshiki; Latta, Mark A; Miyazaki, Masashi

2018-04-01

The relationship between enamel bond fatigue durability and surface free-energy characteristics with universal adhesives was investigated. The initial shear bond strengths and shear fatigue strengths of five universal adhesives to enamel were determined with and without phosphoric acid pre-etching. The surface free-energy characteristics of adhesive-treated enamel with and without pre-etching were also determined. The initial shear bond strength and shear fatigue strength of universal adhesive to pre-etched enamel were higher than those to ground enamel. The initial shear bond strength and shear fatigue strength of universal adhesive to pre-etched enamel were material dependent, unlike those to ground enamel. The surface free-energy of the solid (γ S ) and the hydrogen-bonding force (γSh) of universal adhesive-treated enamel were different depending on the adhesive, regardless of the presence or absence of pre-etching. The bond fatigue durability of universal adhesives was higher to pre-etched enamel than to ground enamel. In addition, the bond fatigue durability to pre-etched enamel was material dependent, unlike that to ground enamel. The surface free-energy characteristics of universal adhesive-treated enamel were influenced by the adhesive type, regardless of the presence or absence of pre-etching. The surface free-energy characteristics of universal adhesive-treated enamel were related to the results of the bond fatigue durability. © 2018 Eur J Oral Sci.

Influence of surface treatment on shear bond strength of orthodontic brackets

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Ione Helena Vieira Portella Brunharo

2013-06-01

Full Text Available INTRODUCTION: The shear bond strength of orthodontic brackets bonded to micro-hybrid and micro-particulate resins under different surface treatment methods was assessed. METHODS: Two hundred and eighty test samples were divided into 28 groups (n = 10, where 140 specimens were filled with Durafill micro-particulate resin and 140 with Charisma composite. In 140 samples, a coupling agent (silane was applied. The surface treatment methods were: Phosphoric and hydrofluoric acid etching, sodium bicarbonate and aluminum oxide blasting, stone and burs. A Universal Instron Machine was used to apply an occlusal shear force directly to the resin composite bracket surface at a speed of 0.5 mm/min. The means were compared using analysis of variance and multivariate regression to assess the interaction between composites and surface treatment methods. RESULTS: Means and standard deviations for the groups were: Sodium bicarbonate jet 11.27±2.78; burs 9.26±3.01; stone 7.95±3.67; aluminum oxide blasting 7.04±3.21; phosphoric acid 5.82±1.90; hydrofluoric acid 4.54±2.87, and without treatment 2.75±1.49. An increase of 1.94 MPa in shear bond strength was seen in Charisma groups. Silane agent application reduced the Charisma shear bond strength by 0.68 Mpa, but increased Durafill means for bicarbonate blasting (0.83, burs (0.98 and stone drilling (0.46. CONCLUSION: The sodium bicarbonate blasting, burs and stone drilling methods produced adequate shear bond strength and may be suitable for clinical use. The Charisma micro hybrid resin composite showed higher shear bond means than Durafill micro particle composite.

Influence of surface treatment on shear bond strength of orthodontic brackets.

Science.gov (United States)

Brunharo, Ione Helena Vieira Portella; Fernandes, Daniel Jogaib; de Miranda, Mauro Sayão; Artese, Flavia

2013-01-01

The shear bond strength of orthodontic brackets bonded to micro-hybrid and micro-particulate resins under different surface treatment methods was assessed. Two hundred and eighty test samples were divided into 28 groups (n = 10), where 140 specimens were filled with Durafill micro-particulate resin and 140 with Charisma composite. In 140 samples, a coupling agent (silane) was applied. The surface treatment methods were: Phosphoric and hydrofluoric acid etching, sodium bicarbonate and aluminum oxide blasting, stone and burs. A Universal Instron Machine was used to apply an occlusal shear force directly to the resin composite bracket surface at a speed of 0.5 mm/min. The means were compared using analysis of variance and multivariate regression to assess the interaction between composites and surface treatment methods. Means and standard deviations for the groups were: Sodium bicarbonate jet 11.27 ± 2.78; burs 9.26 ± 3.01; stone 7.95 ± 3.67; aluminum oxide blasting 7.04 ± 3.21; phosphoric acid 5.82 ± 1.90; hydrofluoric acid 4.54 ± 2.87, and without treatment 2.75 ± 1.49. An increase of 1.94 MPa in shear bond strength was seen in Charisma groups. Silane agent application reduced the Charisma shear bond strength by 0.68 Mpa, but increased Durafill means for bicarbonate blasting (0.83), burs (0.98) and stone drilling (0.46). The sodium bicarbonate blasting, burs and stone drilling methods produced adequate shear bond strength and may be suitable for clinical use. The Charisma micro hybrid resin composite showed higher shear bond means than Durafill micro particle composite.

The Effect of Bond Albedo on Venus' Atmospheric and Surface Temperatures

Science.gov (United States)

Bullock, M. A.; Limaye, S. S.; Grinspoon, D. H.; Way, M.

2017-12-01

In spite of Venus' high planetary albedo, sufficient solar energy reaches the surface to drive a powerful greenhouse effect. The surface temperature is three times higher than it would be without an atmosphere. However, the details of the energy balance within Venus' atmosphere are poorly understood. Half of the solar energy absorbed within the clouds, where most of the solar energy is absorbed, is due to an unknown agent. One of the challenges of modeling Venus' atmosphere has been to account for all the sources of opacity sufficient to generate a globally averaged surface temperature of 735 K, when only 2% of the incoming solar energy is deposited at the surface. The wavelength and spherically integrated albedo, or Bond albedo, has typically been cited as between 0.7 and 0.82 (Colin 1983). Yet, recent photometry of Venus at extended phase angles between 2 and 179° indicate a Bond albedo of 0.90 (Mallama et al., 2006). The authors note an increase in cloud top brightness at phase angles fixed. Figure 1b (right). Venus surface temperature as Bond Albedo changes. Radiative-convective equilibrium models predict the correct globally averaged surface temperature at a=0.81. Calculations here show that a Bond albedo of a=0.9 would yield a surface temperature of 666.4 K, about 70 K too low, unless there is additional thermal absorption within the atmosphere that is not understood. Colin, L.,, Venus, University of Arizona Press, Tucson, 1983, pp 10-26. Mallama, A., et al., 2006. Icarus. 182, 10-22.

Bond strengths of brackets bonded to enamel surfaces conditioned with femtosecond and Er:YAG laser systems.

Science.gov (United States)

Aglarci, Cahide; Demir, Necla; Aksakalli, Sertac; Dilber, Erhan; Sozer, Ozlem Akinci; Kilic, Hamdi Sukur

2016-08-01

The aim of this study was to compare femtosecond and Er:YAG laser systems with regard to enamel demineralization and bracket bond strength. Human-extracted premolars were randomized to three groups (n = 17) depending on the conditioning treatment used for the buccal surfaces: 37 % orthophosphoric acid, Er:YAG laser etching (MSP mode 120 mJ, 10 Hz, 1.2 W), and femtosecond laser etching (0.4 W, 800 nm, 90 fs/pulse, 1 kHz). Metal brackets were bonded with Transbond XT to the conditioned surfaces and light cured for 20 s. The samples were thermocycled (5000 cycles, 5-55 °C) and subjected to shear bond strength (SBS) testing using a universal testing machine. Failure types were analyzed under an optical stereomicroscope and SEM. The adhesive remnant index (ARI) was evaluated to assess residual adhesive on the enamel surface. The results revealed no significant differences in SBS between the Er:YAG laser (7.2 ± 3.3 MPa) and acid etching groups (7.3 ± 2.7 MPa; p enamel interface.

The Effect of Nylon and Polyester Peel Ply Surface Preparation on the Bond Quality of Composite Laminates

Science.gov (United States)

Moench, Molly K.

The preparation of the surfaces to be bonded is critical to the success of composite bonds. Peel ply surface preparation is attractive from a manufacturing and quality assurance standpoint, but is a well known example of the extremely system-specific nature of composite bonds. This study examined the role of the surface energy, morphology, and chemistry left by peel ply removal in resulting bond quality. It also evaluated the use of contact angle surface energy measurement techniques for predicting the resulting bond quality of a prepared surface. The surfaces created by preparing three aerospace fiber-reinforced composite prepregs were compared when prepared with a nylon vs a polyester peel ply. The prepared surfaces were characterized with contact angle measurements with multiple fluids, scanning electron microscopy (SEM), and x-ray electron spectroscopy. The laminates were bonded with aerospace grade film adhesives. Bond quality was assessed via double cantilever beam testing followed by optical and scanning electron microscopy of the fracture surfaces.The division was clear between strong bonds (GIC of 600- 1000J/m2 and failure in cohesion) and weak bonds (GIC of 80-400J/m2 and failure in adhesion). All prepared laminates showed the imprint of the peel ply texture and evidence of peel ply remnants after fabric removal, either through SEM or XPS. Within an adhesive system, large amounts of SEM-visible peel ply material transfer correlated with poor bond quality and cleaner surfaces with higher bond quality. The both sides of failed weak bonds showed evidence of peel ply remnants under XPS, showing that at least some failure is occurring through the remnants. The choice of adhesive was found to be significant. AF 555 adhesive was more tolerant of peel ply contamination than MB 1515-3. Although the bond quality results varied substantially between tested combinations, the total surface energies of all prepared surfaces were very similar. Single fluid contact angle

Theoretical study of ZnO adsorption and bonding on Al2O3 (0001) surface

Institute of Scientific and Technical Information of China (English)

LI Yanrong; YANG Chun; XUE Weidong; LI Jinshan; LIU Yonghua

2004-01-01

ZnO adsorption on sapphire (0001) surface is theoretically calculated by using a plane wave ultrasoft pseudo-potential method based on ab initio molecular dynamics. The results reveal that the surface relaxation in the first layer Al-O is reduced, even eliminated after the surface adsorption of ZnO, and the chemical bonding energy is 434.3(±38.6) kJ·mol-1. The chemical bond of ZnO (0.185 ± 0.01 nm) has a 30° angle away from the adjacent Al-O bond, and the stable chemical adsorption position of the Zn is deflected from the surface O-hexagonal symmetry with an angle of about 30°. The analysis of the atomic populations, density of state and bonding electronic density before and after the adsorption indicates that the chemical bond formed by the O2- of the ZnO and the surface Al3+ has a strong ionic bonding characteristic, while the chemical bond formed by the Zn2+ and the surface O2- has an obvious covalent characteristic, which comes mainly from the hybridization of the Zn 4s and the O 2p and partially from that of the Zn 3d and the O 2p.

Chemical bond activation observed with an x-ray laser

International Nuclear Information System (INIS)

Beye, Martin; Öberg, Henrik; Xin, Hongliang

2016-01-01

The concept of bonding and anti-bonding orbitals is fundamental in chemistry. The population of those orbitals and the energetic difference between the two reflect the strength of the bonding interaction. Weakening the bond is expected to reduce this energetic splitting, but the transient character of bond-activation has so far prohibited direct experimental access. Lastly, we apply time-resolved soft X-ray spectroscopy at a free-electron laser to directly observe the decreased bonding–anti-bonding splitting following bond-activation using an ultra short optical laser pulse.

Effect of Nd: YAG laser irradiation on surface properties and bond strength of zirconia ceramics.

Science.gov (United States)

Liu, Li; Liu, Suogang; Song, Xiaomeng; Zhu, Qingping; Zhang, Wei

2015-02-01

This study investigated the effect of neodymium-doped yttrium aluminum garnet (Nd: YAG) laser irradiation on surface properties and bond strength of zirconia ceramics. Specimens of zirconia ceramic pieces were divided into 11 groups according to surface treatments as follows: one control group (no treatment), one air abrasion group, and nine laser groups (Nd: YAG irradiation). The laser groups were divided by applying with different output power (1, 2, or 3 W) and irradiation time (30, 60, or 90 s). Following surface treatments, the morphological characteristics of ceramic pieces was observed, and the surface roughness was measured. All specimens were bonded to resin cement. After, stored in water for 24 h and additionally aged by thermocycling, the shear bond strength was measured. Dunnett's t test and one-way ANOVA were performed as the statistical analyses for the surface roughness and the shear bond strength, respectively, with α = .05. Rougher surface of the ceramics could be obtained by laser irradiation with higher output power (2 and 3 W). However, cracks and defects were also found on material surface. The shear bond strength of laser groups was not obviously increased, and it was significantly lower than that of air abrasion group. No significant differences of the shear bond strength were found among laser groups treated with different output power or irradiation time. Nd: YAG laser irradiation cannot improve the surface properties of zirconia ceramics and cannot increase the bond strength of the ceramics. Enhancing irradiation power and extending irradiation time cannot induce higher bond strength of the ceramics and may cause material defect.

Influence of surface treatments on the shear bond strength of orthodontic brackets to porcelain

Science.gov (United States)

Wang, Cong; Zeng, Jishan; Wang, Shaoan; Yang, Zheng; Huang, Qian; Chen, Pixiu; Zhou, Shujuan; Liu, Xiaoqing

2008-11-01

The purpose of this study was to investigate the effect of various surface treatments after different storage time and thermocycling on the shear bond strength of orthodontic brackets to the feldspathic porcelain surfaces. 128 disc-shaped porcelain specimens were randomly assigned to the following surface treatments: 9.6% HFA, 9.6% HFA combined with silane, 50 μ aluminum trioxide sandblasting followed by silane and application of silane after 37% phosphoric acid. Metal or ceramic brackets were bonded onto each treated porcelain facet with light cured resin. The samples were stored in 37 °C water 1 day or 7 days, thermocycled 500 times from 5 to 55 °C. The shear bond strengths were measured (1 mm/min), and statistically analyzed. The bond failure sites were classified according to ARI system. The surface of the glazed, sandblasted, hydrofluoric and phosphoric acid etched porcelain were examined with SEM. All groups achieved reasonable bond strengths to withstand the application of orthodontic forces. Water storage for 7 days caused lower shear bond strength than that of 1 day. But there is no statistically significant difference between the two groups. The mean shear bond strength provided by ceramic bracket with mechanical retention had no statistical difference with that of metal bracket. Therefore, the optimal treatment for orthodontic brackets bonding to feldspathic porcelain was to apply phosphoric acid combined with silane.

EFFECT OF SURFACE CONDTIONINGON BOND STRENGTH TO ENAMEL AND DENTIN

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M MOUSAVINASAB

2002-09-01

Full Text Available Introduction. Compoglass is a trade mark of dental compomers and because of its partially resinus structure, surface conditioning of dental surfaces is needed for a better bonding process. In this study, the effect of enamel and dentin conditioning procedure on shear bond strength (SBS of compoglass to tooth surfaces was studied. Methods. four groups each one including 11 sound premolars were chosen and their surfaces were prepared as following groups: group1, unconitioned dentin; group 2, dentin conditioning with phosphoric acid 35%; group 3, dentin conditioning with polyacrylic acid 20% group 4, unconditioning enamel; group 5, enamel conditioning with phosphoric acid 35%; and group 6, enamel conditioning with polyacrylic acid 20%. Compoglass was bonded to prepared surfaces and after fixation of the samples in acrylic molds, all samples were tested under shear force of instron testing machine at a rate of 1 mm/min speed. Results. The mean SBS obtained in these 6 groups were 6.207, 8.057, 10.146, 25.939 and 11.827 mpa. the mode of fracture also studied using a streomicroscope. Statistical analysis of the results showed that the maximum SBS obtained in group 5 and the lowest SBS about 6.207 mpa obtained in group 1. Despite increase in SBS group 2 and 3, there was no statistical differncies between group 1, 2 and 3. Discussion. Based on results of this study, conditioning of enamel and dentin surface due to improve SBS is recommeneded.

Influence of air-powder polishing on bond strength and surface-free energy of universal adhesive systems.

Science.gov (United States)

Tamura, Yukie; Takamizawa, Toshiki; Shimamura, Yutaka; Akiba, Shunsuke; Yabuki, Chiaki; Imai, Arisa; Tsujimoto, Akimasa; Kurokawa, Hiroyasu; Miyazaki, Masashi

2017-11-29

The influences of air-powder polishing with glycine or sodium bicarbonate powders on shear bond strengths (SBS) and surface-free energies of universal adhesives were examined. Scotchbond Universal Adhesive (SU, 3M ESPE), G-Premio Bond (GP, GC), Adhese Universal (AU, Ivoclar Vivadent), and All-Bond Universal (AB, Bisco) were used in this study. Bovine dentin surfaces were air polished with glycine or sodium bicarbonate powders prior to the bonding procedure, and resin pastes were bonded to the dentin surface using universal adhesives. SBSs were determined after 24-h storage in distilled water at 37°C. Surface-free energy was then determined by measuring contact angles using three test liquids on dentin surfaces. Significantly lower SBSs were observed for dentin that was air-powder polished and surface-free energies were concomitantly lowered. This study indicated that air-powder polishing influences SBSs and surface-free energies. However, glycine powder produced smaller changes in these surface parameters than sodium bicarbonate.

Enhancement of surface magnetism due to bulk bond dilution

International Nuclear Information System (INIS)

Tsallis, C.; Sarmento, E.F.; Albuquerque, E.L. de

1985-01-01

Within a renormalization group scheme, the phase diagram of a semi-infinite simple cubic Ising ferromagnet is discussed, with arbitrary surface and bulk coupling constants, and including possible dilution of the bulk bonds. It is obtained that dilution makes easier the appearance of surface magnetism in the absence of bulk magnetism. (Author) [pt

Tensile bond strength of hydroxyethyl methacrylate dentin bonding agent on dentin surface at various drying techniques

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Kun Ismiyatin

2010-06-01

Full Text Available Background: There are several dentin surface drying techniques to provide a perfect resin penetration on dentin. There are two techniques which will be compared in this study. The first technique was by rubbing dentin surface gently using cotton pellet twice, this technique is called blot dry technique. The second technique is by air blowing dentin surface for one second and continued by rubbing dentin surface gently using moist cotton. Purpose: This experiment was aimed to examine the best dentin surface drying techniques after 37% phosphoric acid etching to obtain the optimum tensile bond strength between hydroxyethyl methacrylate (HEMA and dentin surface. Method: Bovine teeth was prepared flat to obtain the dentin surface and than was etched using 37% phosphoric acid for 15 seconds. After etching the dentin was cleaned using 20 cc plain water and dried with blot dry techniques (group I, or dried with air blow for one second (group II, or dried with air blow for one second, and continued with rubbing gently using moist cotton pellet (group III, and without any drying as control group (group IV. After these drying, the dentin surfaces were applied with resin dentin bonding agent and put into plunger facing the composite mould. The antagonist plunger was filled with composite resin. After 24 hours, therefore bond strength was measured using Autograph. Result: Data obtained was analyzed using One-Way ANOVA with 95% confidence level and continued with LSD test on p≤0.05. The result showed that the highest tensile bond strength was on group I, while the lowest on group IV. Group II and IV, III and IV, II and III did not show signigicant difference (p>0.05. Conclusion: Dentin surface drying techniques through gentle rubbing using cotton pellet twice (blot dry technique gave the greatest tensile bond strength.Latar belakang masalah: Tehnik pengeringan permukaan dentin agar resin dapat penetrasi dengan sempurna adalah dengan cara pengusapan secara

Effect of Pd Surface Roughness on the Bonding Process and High Temperature Reliability of Au Ball Bonds

Science.gov (United States)

Huang, Y.; Kim, H. J.; McCracken, M.; Viswanathan, G.; Pon, F.; Mayer, M.; Zhou, Y. N.

2011-06-01

A 0.3- μm-thick electrolytic Pd layer was plated on 1 μm of electroless Ni on 1 mm-thick polished and roughened Cu substrates with roughness values ( R a) of 0.08 μm and 0.5 μm, respectively. The rough substrates were produced with sand-blasting. Au wire bonding on the Ni/Pd surface was optimized, and the electrical reliability was investigated under a high temperature storage test (HTST) during 800 h at 250°C by measuring the ball bond contact resistance, R c. The average value of R c of optimized ball bonds on the rough substrate was 1.96 mΩ which was about 40.0% higher than that on the smooth substrate. The initial bondability increased for the rougher surface, so that only half of the original ultrasonic level was required, but the reliability was not affected by surface roughness. For both substrate types, HTST caused bond healing, reducing the average R c by about 21% and 27%, respectively. Au diffusion into the Pd layer was observed in scanning transmission electron microscopy/ energy dispersive spectroscopy (STEM-EDS) line-scan analysis after HTST. It is considered that diffusion of Au or interdiffusion between Au and Pd can provide chemically strong bonding during HTST. This is supported by the R c decrease measured as the aging time increased. Cu migration was indicated in the STEM-EDS analysis, but its effect on reliability can be ignored. Au and Pd tend to form a complete solid solution at the interface and can provide reliable interconnection for high temperature (250°C) applications.

Evaluation of Surface Characteristics and Shear Bond Strength of Metal Brackets Bonded to Two Different Porcelain Systems (Feldspathic/IPS-Empress-2 treated with Different Surface Conditioning Methods

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Amal S Nair

2012-01-01

Conclusion: Surface conditioning with Co-Jet sand which produced silicatization resulted in a favorable bond strength in both feldspathic and IPS-Empress-2 ceramic surfaces. It was shown that it produced the least surface roughness among all the other surface conditioning groups.

Comparison of bond strengths of ceramic brackets bonded to zirconia surfaces using different zirconia primers and a universal adhesive.

Science.gov (United States)

Lee, Ji-Yeon; Ahn, Jaechan; An, Sang In; Park, Jeong-Won

2018-02-01

The aim of this study is to compare the shear bond strengths of ceramic brackets bonded to zirconia surfaces using different zirconia primers and universal adhesive. Fifty zirconia blocks (15 × 15 × 10 mm, Zpex, Tosoh Corporation) were polished with 1,000 grit sand paper and air-abraded with 50 µm Al 2 O 3 for 10 seconds (40 psi). They were divided into 5 groups: control (CO), Metal/Zirconia primer (MZ, Ivoclar Vivadent), Z-PRIME Plus (ZP, Bisco), Zirconia Liner (ZL, Sun Medical), and Scotchbond Universal adhesive (SU, 3M ESPE). Transbond XT Primer (used for CO, MZ, ZP, and ZL) and Transbond XT Paste was used for bracket bonding (Gemini clear ceramic brackets, 3M Unitek). After 24 hours at 37°C storage, specimens underwent 2,000 thermocycles, and then, shear bond strengths were measured (1 mm/min). An adhesive remnant index (ARI) score was calculated. The data were analyzed using one-way analysis of variance and the Bonferroni test ( p = 0.05). Surface treatment with primers resulted in increased shear bond strength. The SU group showed the highest shear bond strength followed by the ZP, ZL, MZ, and CO groups, in that order. The median ARI scores were as follows: CO = 0, MZ = 0, ZP = 0, ZL = 0, and SU = 3 ( p < 0.05). Within this experiment, zirconia primer can increase the shear bond strength of bracket bonding. The highest shear bond strength is observed in SU group, even when no primer is used.

Excellent bonding behaviour of novel surface-tailored fibre ...

Indian Academy of Sciences (India)

Administrator

tured completely before pull-out, leading to full utilization of its tensile strength, and ... Composite rods; surface tailoring; cementitious matrix; pull-out test; bonding characteristics. 1. ... machine (Lloyd LR50K) at a speed of 0∙5 mm/min with a.

Bond-selective control of a gas-surface reaction

Science.gov (United States)

Killelea, Daniel R.

The prospect of using light to selectively control chemical reactions has tantalized chemists since the development of the laser. Unfortunately, the realization of laser-directed chemistry is frequently thwarted by the randomization of energy within the molecule through intramolecular vibrational energy distribution (IVR). However, recent results showing vibrational mode-specific reactivity on metal surfaces suggest that IVR may not always be complete for gas-surface reactions. Here, we combine molecular beam techniques and direct laser excitation to characterize the bond-specific reactivity of trideuteromethane on a Ni(111) surface. Our results reveal important details about how vibrational energy is distributed in the reactive molecule. We use a molecular beam to direct state-selected trideuteromethane (CHD 3) molecules onto a nickel single crystal sample and use the results we obtain to describe the flow of vibrational energy in the methane-surface reaction complex. We show that CHD3 molecules initially excited to v=1, J=2, K=0 of the v 1 symmetric C-H stretching mode will dissociate exclusively via C-H cleavage on Ni(111). This result highlights the localization of vibrational energy in the reaction complex, despite the presence of many energy exchange channels with the high state-density surface. We demonstrate, for the first time, highly parallel bond-selective control of a heterogeneously catalyzed reaction. We place our results in the context of recent experiments investigating IVR for molecules in both the gas phase and liquid solutions. If IVR is fast on the reaction timescale, vibrational energy would be randomly distributed throughout the nascent methane-surface reaction complex and vibrational mode-specific behavior would not occur. The short timescale of a direct gas-surface collision may explain how the exchange of energy via IVR is limited to only a small subset of the energetic configurations available to the reaction complex. This framework

The effect of different surface treatments of stainless steel crown and different bonding agents on shear bond strength of direct composite resin veneer

Directory of Open Access Journals (Sweden)

Ajami B

2007-01-01

Full Text Available Background and Aim: Stainless steel crown (SSC is the most durable and reliable restoration for primary teeth with extensive caries but its metalic appearance has always been a matter of concern. With advances in restorative materials and metal bonding processes, composite veneer has enhanced esthetics of these crowns in clinic. The aim of this study was to evaluate the shear bond strength of SSC to composite resin using different surface treatments and adhesives. Materials and Methods: In this experimental study, 90 stainless steel crowns were selected. They were mounted in molds and divided into 3 groups of 30 each (S, E and F. In group S (sandblast, buccal surfaces were sandblasted for 5 seconds. In group E (etch acidic gel was applied for 5 minutes and in group F (fissure bur surface roughness was created by fissure diamond bur. Each group was divided into 3 subgroups (SB, AB, P based on different adhesives: Single Bond, All Bond2 and Panavia F. Composite was then bonded to specimens. Cases were incubated in 100% humidity at 37°C for 24 hours. Shear bond strength was measured by Zwick machine with crosshead speed of 0.5 mm/min. Data were analyzed by ANOVA test with p0.05 so the two variables were studied separately. No significant difference was observed in mean shear bond strength of composite among the three kinds of adhesives (P>0.05. Similar results were obtained regarding surface treatments (P>0.05. Conclusion: Based on the results of this study, treating the SSC surface with bur and using single bond adhesive and composite can be used successfully to obtain esthetic results in pediatric restorative treatments.

Diffusion bonding of reduced activation ferritic steel F82H for demo blanket application

International Nuclear Information System (INIS)

Kurasawa, T.; Tamura, M.

1996-01-01

A reduced activation ferritic steel, a grade F82H developed by JAERI, is a promising candidate structural material for the blanket and the first wall of DEMO reactors. In the present study, diffusion bonding of F82H has been investigated to develop the fabrication procedures of the blanket box and the first wall panel with cooling channels embedded by F82H. The parameters examined are the bonding temperature (810-1050 C), bonding pressure (2-10 MPa) and roughness of the bonding surface (0.5-12.8 μR max ), and metallurgical examination and mechanical tests of the diffusion bonded joints have been conducted. From the tests, sufficient bonding was obtained under the temperatures of 840-1 050 C (compressive stress of 3-12 MPa), and it was found that heat treatment following diffusion bonding is essential to obtain the mechanical properties similar to that of the base metal. (orig.)

Disulfide bond within mu-calpain active site inhibits activity and autolysis.

Science.gov (United States)

Lametsch, René; Lonergan, Steven; Huff-Lonergan, Elisabeth

2008-09-01

Oxidative processes have the ability to influence mu-calpain activity. In the present study the influence of oxidation on activity and autolysis of mu-calpain was examined. Furthermore, LC-MS/MS analysis was employed to identify and characterize protein modifications caused by oxidation. The results revealed that the activity of mu-calpain is diminished by oxidation with H2O2 in a reversible manner involving cysteine and that the rate of autolysis of mu-calpain concomitantly slowed. The LC-MS/MS analysis of the oxidized mu-calpain revealed that the amino acid residues 105-133 contained a disulfide bond between Cys(108) and Cys(115). The finding that the active site cysteine in mu-calpain is able to form a disulfide bond has, to our knowledge, not been reported before. This could be part of a unique oxidation mechanism for mu-calpain. The results also showed that the formation of the disulfide bond is limited in the control (no oxidant added), and further limited in a concentration-dependent manner when beta-mercaptoethanol is added. However, the disulfide bond is still present to some extent in all conditions indicating that the active site cysteine is potentially highly susceptible to the formation of this intramolecular disulfide bond.

Surface topography and bond strengths of feldspathic porcelain prepared using various sandblasting pressures.

Science.gov (United States)

Moravej-Salehi, Elham; Moravej-Salehi, Elahe; Valian, Azam

2016-11-01

The purpose of this study was to determine the bond strength of composite resin to feldspathic porcelain and its surface topography after sandblasting at different pressures. In this in vitro study, 68 porcelain disks were fabricated and randomly divided into four groups of 17. The porcelain surface in group 1 was etched with hydrofluoric acid. Groups 2, 3, and 4 were sandblasted at 2, 3 and 4 bars pressure, respectively. Surface topography of seven samples in each of the four groups was examined by a scanning electron microscope (SEM). The remaining 40 samples received the same silane agent, bonding agent, and composite resin and they were then subjected to 5000 thermal cycles and evaluated for shear bond strength. Data were analyzed using one-way anova. The mode of failure was determined using stereomicroscope and SEM. The highest shear bond strength was seen in group 4. however, statistically significant differences were not seen between the groups (P = 0.780). The most common mode of failure was cohesive in porcelain. The SEM showed different patterns of hydrofluoric acid etching and sandblasting. Increasing the sandblasting pressure increased the surface roughness of feldspathic porcelain but no difference in bond strength occurred. © 2015 Wiley Publishing Asia Pty Ltd.

Material and orientation dependent activity for heterogeneously catalyzed carbon-bromine bond homolysis

Energy Technology Data Exchange (ETDEWEB)

Walch, Hermann; Gutzler, Rico; Sirtl, Thomas; Eder, Georg; Lackinger, Markus [LMU Munich, Section Crystallography (Germany)

2010-07-01

Adsorption of the organic molecule 1,3,5-tris(4-bromophenyl)benzene on different metallic substrates, namely Cu(111), Ag(111) and Ag(110) has been studied by variable temperature Scanning Tunneling Microscopy (STM). Depending on substrate temperature, material and orientation, we observe a surface-catalyzed dehalogenation reaction. Deposition onto the catalytically active substrates Cu(111) and Ag(110) held at room temperature leads to cleavage of the carbon-bromine bonds and subsequent formation of protopolymers, i.e radical metal coordination complexes. However upon deposition on Ag(111) no such reaction has been observed. Instead, various self-assembled ordered structures based on intact molecules could be identified. Also sublimation onto either substrate held at 80 K did not result in any dehalogenation, thereby exemplifying that the dehalogenation reaction is thermally activated. We explain the differences in catalytic activity by charge transfer into unoccupied molecular orbitals and subsequent destabilization of the C-Br bond, whereby enhanced molecule-substrate interaction leads to an increasing magnitude of charge transfer. The interaction strength follows the general reactivity order Cu>Ag>Au for (111) faces and is generally enhanced on higher corrugated surfaces as the (110) facet in case of fcc substrates.

On analogy between surface fracture energy and activaiton energy of bonding in solid phase

International Nuclear Information System (INIS)

Shatinsky, V.F.; Kopylov, V.I.

1976-01-01

This article makes an attempt on the basis of experimental data to compare the processes of failure and formation of a bond by comparing the energy consumptions going in one case or another into initial plastic deformation of a certain volume and the further interatomic interaction at the boundary (separation, formation of the bond). Two values characterizing the different processes - the unit failure energy γ and the activation energy for the formation of a bond Q - are compared. It has been established that the energy consumed for plastic deformation and adhesion interaction of atoms on the surface of microprojections and providing the formation of a bond in the solid-phase condition is close to the specific failure energy. The equality of energies consumed for the formation of a bond and failure allows to make use of any of those characteristics to calculate parameters of processes of the formation of a bond and failure. It seems to be convenient in the analysis of the failure process at a temperature when the ductility is high and methodically, the crack propagation is hard to investigate, in particular to estimate the volume of the preliminary failure zone. Having determined γ from the contact interaction data, the strength characteristics can be evaluated. (author)

Control of chemical bonding of the ZnO surface grown by molecular beam epitaxy

International Nuclear Information System (INIS)

Ogata, K.; Komuro, T.; Hama, K.; Koike, K.; Sasa, S.; Inoue, M.; Yano, M.

2004-01-01

Toward the fabrication of enzyme modified field effect transistors (EnFETs) as one of organic/inorganic hybridized structures, surface bonding of the ZnO grown by molecular beam epitaxy was controlled by ex situ treatments. Angle resolved X-ray photoelectron spectroscopy (XPS) measurement revealed that O-H bonds exist at the surface of ZnO. It was found that the number of O-H bond could be changed with reversibility using plasma and thermal treatments

Innovative Approaches To Improving The Bond Between Concrete and Steel Surfaces

National Research Council Canada - National Science Library

Day, Donna C; Carrasquillo, Mariangelica; Weiss, Jr., Charles A; Sykes, Melvin C; Baugher, Jr., Earl H; Malone, Philip G

2006-01-01

A reactive silicate layer fused onto the surface of reinforcing steel provides a coupling layer that allows a very strong bond to develop between hydrating Portland cement paste and the surface of the steel...

Porcelain surface alterations and refinishing after use of two orthodontic bonding methods.

Science.gov (United States)

Herion, Drew T; Ferracane, Jack L; Covell, David A

2010-01-01

To compare porcelain surfaces at debonding after use of two surface preparation methods and to evaluate a method for restoring the surface. Lava Ceram feldspathic porcelain discs (n = 40) underwent one of two surface treatments prior to bonding orthodontic brackets. Half the discs had sandblasting, hydrofluoric acid, and silane (SB + HF + S), and the other half, phosphoric acid and silane (PA + S). Brackets were debonded using bracket removing pliers, and resin was removed with a 12-fluted carbide bur. The surface was refinished using a porcelain polishing kit, followed by diamond polishing paste. Measurements for surface roughness (Ra), gloss, and color were made before bonding (baseline), after debonding, and after each step of refinishing. Surfaces were also examined by scanning electron microscopy (SEM). Data was analyzed with 2-way ANOVA followed by Tukey HSD tests (alpha = 0.05). The SB + HF + S bonding method increased Ra (0.160 to 1.121 microm), decreased gloss (41.3 to 3.7) and altered color (DeltaE = 4.37; P gloss (41.7 to 38.0) and color (DeltaE = 0.50). The measurements and SEM observations showed that changes were fully restored to baseline with refinishing. The PA + S method caused significantly less damage to porcelain than the SB + HF + S method. The refinishing protocol fully restored the porcelain surfaces.

A study of laser surface treatment in bonded repair of composite aircraft structures.

Science.gov (United States)

Li, Shaolong; Sun, Ting; Liu, Chang; Yang, Wenfeng; Tang, Qingru

2018-03-01

Surface pre-treatment is one of the key processes in bonded repair of aircraft carbon fibre reinforced polymer composites. This paper investigates the surface modification of physical and chemical properties by laser ablation and conventional polish treatment techniques. Surface morphology analysed by laser scanning confocal microscopy and scanning electron microscopy showed that a laser-treated surface displayed higher roughness than that of a polish-treated specimen. The laser-treated laminate exhibited more functional groups in the form of O 1 s/C 1 s atomic ratio of 30.89% for laser-treated and 20.14% for polish-treated as evidenced by X-ray photoelectron spectroscopy observation. Contact angle goniometry demonstrated that laser treatment can provide increased surface free energy and wettability. In the light of mechanical interlocking, molecular bonding and thermodynamics theories on adhesion, laser etching process displayed enhanced bonding performance relative to the polishing surface treatment. These properties resulted in an increased single lap shear strength and a cohesive failure mode for laser etching while an adhesive failure mode occurred in polish-treated specimen.

Low-temperature wafer direct bonding of silicon and quartz glass by a two-step wet chemical surface cleaning

Science.gov (United States)

Wang, Chenxi; Xu, Jikai; Zeng, Xiaorun; Tian, Yanhong; Wang, Chunqing; Suga, Tadatomo

2018-02-01

We demonstrate a facile bonding process for combining silicon and quartz glass wafers by a two-step wet chemical surface cleaning. After a post-annealing at 200 °C, strong bonding interfaces with no defects or microcracks were obtained. On the basis of the detailed surface and bonding interface characterizations, the bonding mechanism was explored and discussed. The amino groups terminated on the cleaned surfaces might contribute to the bonding strength enhancement during the annealing. This cost-effective bonding process has great potentials for silicon- and glass-based heterogeneous integrations without requiring a vacuum system.

Investigation of Surface Pre-Treatment Methods for Wafer-Level Cu-Cu Thermo-Compression Bonding

Directory of Open Access Journals (Sweden)

Koki Tanaka

2016-12-01

Full Text Available To increase the yield of the wafer-level Cu-Cu thermo-compression bonding method, certain surface pre-treatment methods for Cu are studied which can be exposed to the atmosphere before bonding. To inhibit re-oxidation under atmospheric conditions, the reduced pure Cu surface is treated by H2/Ar plasma, NH3 plasma and thiol solution, respectively, and is covered by Cu hydride, Cu nitride and a self-assembled monolayer (SAM accordingly. A pair of the treated wafers is then bonded by the thermo-compression bonding method, and evaluated by the tensile test. Results show that the bond strengths of the wafers treated by NH3 plasma and SAM are not sufficient due to the remaining surface protection layers such as Cu nitride and SAMs resulting from the pre-treatment. In contrast, the H2/Ar plasma–treated wafer showed the same strength as the one with formic acid vapor treatment, even when exposed to the atmosphere for 30 min. In the thermal desorption spectroscopy (TDS measurement of the H2/Ar plasma–treated Cu sample, the total number of the detected H2 was 3.1 times more than the citric acid–treated one. Results of the TDS measurement indicate that the modified Cu surface is terminated by chemisorbed hydrogen atoms, which leads to high bonding strength.

Effects of moisture conditions of dental enamel surface on bond strength of brackets bonded with moisture-insensitive primer adhesive system.

Science.gov (United States)

Endo, Toshiya; Ozoe, Rieko; Sanpei, Sugako; Shinkai, Koichi; Katoh, Yoshiroh; Shimooka, Shohachi

2008-07-01

The purposes of this study were to evaluate the effects of different degrees of water contamination on the shear bond strength of orthodontic brackets bonded to dental enamel with a moisture-insensitive primer (MIP) adhesive system and to compare the modes of bracket/adhesive failure. A total of 68 human premolars were divided into four groups by primers and enamel surface conditions (desiccated, blot dry, and overwet). In group I, the hydrophobic Transbond XT primer adhesive system was used under desiccated conditions for bonding the brackets; in group II, the hydrophilic Transbond MIP adhesive system was used under desiccated conditions; in group III, the hydrophilic Transbond MIP adhesive system was used under blot dry conditions; and in group IV, the hydrophilic Transbond MIP adhesive system was used under overwet conditions. Shear bond strength was measured with a universal testing machine, and the mode of bracket/adhesive failure was determined according to the adhesive remnant index. The mean shear bond strengths were not significantly different among groups I, II, and III, and were higher than the clinically required range of 6 to 8 MPa. The mean shear bond strength achieved in group IV was significantly lower than that achieved in groups I, II, and III, and also lower than the clinically required values. Bond failure occurred at the enamel-adhesive interface more frequently in group IV than in groups I and III. To achieve clinically sufficient bond strengths with the hydrophilic MIP adhesive system, excess water should be blotted from the water-contaminated enamel surface.

Bonding, Achievement, and Activities: School Bonding, Academic Achievement, and Participation in Extracurricular Activities

Science.gov (United States)

Howard, Anissa K.; Ziomek-Daigle, Jolie

2009-01-01

Utilizing a single-group interrupted time series design (Creswell, 2003), this pilot study examined the relationship between academic achievement, school bonding, and the extracurricular activity participation of "uninvolved" students (n=11) who participated in a voluntary support group at a suburban high school in the southeast. Results…

Environmentally Benign Sol-Gel Surface Treatment for Aluminum Bonding Applications

National Research Council Canada - National Science Library

Osborne, Joseph

1996-01-01

A surface treatment process for aluminum using sol-gel chemistry has been developed that produces strong adhesive bonds without the rinse water requirements of traditional anodizing or etching processes...

Shear-bond-strength of orthodontic brackets to aged nano-hybrid composite-resin surfaces using different surface preparation.

Science.gov (United States)

Demirtas, Hatice Kubra; Akin, Mehmet; Ileri, Zehra; Basciftci, Faruk Ayhan

2015-01-01

The aim of this study was to evaluate the effects of different surface preparation methods on the shear bond strength (SBS) of orthodontic metal brackets to aged nano-hybrid resin composite surfaces in vitro. A total of 100 restorative composite resin discs, 6 mm in diameter and 3 mm thick, were obtained and treated with an ageing procedure. After ageing, the samples were randomly divided as follows according to surface preparation methods: (1)Control, (2)37% phosphoric acid gel, (3)Sandblasting, (4)Diamond bur, (5)Air-flow and 20 central incisor teeth were used for the control etched group. SBS test were applied on bonded metal brackets to all samples. SBS values and residual adhesives were evaluated. Analysis of variance showed a significant difference (porthodontic metal brackets to nano-hybrid composite resin surfaces.

Effect of surface treatments on the bond strengths of facing composite resins to zirconia copings.

Science.gov (United States)

Tsumita, M; Kokubo, Y; Kano, T

2012-09-01

The present study evaluated and compared the bond strength between zirconia and facing composite resin using different surface conditioning methods before and after thermocycling. Four primers, three opaque resins, and two facing composite resins were used, and 10 surface treatment procedures were conducted. The bond strength was measured before and after 4,000 cycles of thermocycling. The mean values of each group were statistically analyzed using one-way analysis of variance (ANOVA). The bond strengths of facing composite resins to zirconia after various treatments varied depending on the primers, opaque resins, body resins, and thermocycling. The application of primers and opaque resins to the zirconia surface after sandblasting is expected to yield strong bond strength of the facing composite resin (Estenia CG&B) even after thermocycling.

Dentin surface treatment using a non-thermal argon plasma brush for interfacial bonding improvement in composite restoration

Science.gov (United States)

Ritts, Andy Charles; Li, Hao; Yu, Qingsong; Xu, Changqi; Yao, Xiaomei; Hong, Liang; Wang, Yong

2010-01-01

The objective of this study is to investigate the treatment effects of non-thermal atmospheric gas plasmas on dentin surfaces for composite restoration. Extracted unerupted human third molars were used by removing the crowns and etching the exposed dentin surfaces with 35% phosphoric acid gel. The dentin surfaces were treated by using a non-thermal atmospheric argon plasma brush for various durations. The molecular changes of the dentin surfaces were analyzed using FTIR/ATR and an increase in carbonyl groups on dentin surfaces was detected with plasma treated dentin. Adper Single Bond Plus adhesive and Filtek Z250 dental composite were applied as directed. To evaluate the dentin/composite interfacial bonding, the teeth thus prepared were sectioned into micro-bars as the specimens for tensile test. Student Newman Keuls tests showed that the bonding strength of the composite restoration to peripheral dentin was significantly increased (by 64%) after 30 s plasma treatment. However, the bonding strength to plasma treated inner dentin did not show any improvement. It was found that plasma treatment of peripheral dentin surface up to 100 s gave an increase in interfacial bonding strength, while a prolong plasma treatment of dentin surfaces, e.g., 5 min treatments, showed a decrease in interfacial bonding strength. PMID:20831586

Effect of Enamel and Dentin Surface Treatment on the Self-Adhesive Resin Cement Bond Strength.

Science.gov (United States)

Mushashe, Amanda Mahmmad; Gonzaga, Carla Castiglia; Cunha, Leonardo Fernandes da; Furuse, Adilson Yoshio; Moro, Alexandre; Correr, Gisele Maria

2016-01-01

The aim of this study was to evaluate the effect of enamel and dentin surface treatment on the micro-shear bond strength of self-adhesive cement. Seventy-two extracted third molars had their crowns embedded in acrylic resin and worn to obtain a flat enamel or dentin surface. The enamel and dentin specimens were randomly assigned to 8 groups (n=12) that were based on surface treatment (11.5% polyacrylic acid solution or no treatment), substrate condition (wet or dry) and storage period (1 day or 90 days), and treated accordingly. Cylinders (1 × 1 mm) were fabricated using self-adhesive resin cement (RelyX U200) following the manufacturer's instructions. The specimens were stored in distilled water at 37 °C for either 1 day or 90 days and subjected to micro-shear bond strength test (EMIC DL 2000 at 0.5 mm/min). After this, the failure type of the specimens was determined. Data were subjected to statistical analysis (a=0.05). According to the results, the 11.5% polyacrylic acid application decreased the bond strength in both enamel and dentin samples. The moist groups showed higher bond strength than the dry ones, regardless of the substrate and surface treatment. Storage period did not influence bond strength. In conclusion, surface treatment with 11.5% polyacrylic acid and absence of moisture decreased the bond strength of the resin-cement (RelyU200), regardless of the storage period.

[Effects of different surface treatments on the zirconia-resin cement bond strength].

Science.gov (United States)

Liao, Y; Liu, X Q; Chen, L; Zhou, J F; Tan, J G

2018-02-18

To evaluate the effects of different surface treatments on the shear bond strength between zirconia and resin cement. Forty zirconia discs were randomly divided into four groups (10 discs in each group) for different surface treatments: control, no surface treatment; sandblast, applied air abrasion with aluminum oxide particles; ultraviolet (UV), the zirconia sample was placed in the UV sterilizer at the bottom of the UV lamp at 10 mm, and irradiated for 48 h; cold plasma, the discs were put in the cold plasma cabinet with the cold plasma generated from the gas of He for 30 s. Specimens of all the groups were surface treated prior to cementation with Panavia F 2.0 cement. The surface morphology and contact angle of water were measured. The shear bond strengths were tested and the failure modes were examined with a stereomicroscope. Surface morphology showed no difference between the UV/cold plasma group and the control group. Sandblasted zirconia displayed an overall heterogeneous distribution of micropores. The contact angle of the control group was 64.1°±2.0°. After sandblasting, UV irradiation and cold plasma exposure, the values significantly decreased to 48.8°±2.6°, 27.1°±3.6° and 32.0°±3.3°. The values of shear bond strength of the specimens with sandblasted (14.82±2.01) MPa were higher than those with no treatment (9.41±1.07) MPa with statistically significant difference (Pbond strength of the specimens with UV irradiation (10.02±0.64) MPa were higher than those with no treatment (9.41±1.07) MPa, but without statistically significant difference (P>0.05). The values of cold plasma group (18.34±3.05) MPa were significantly higher than those of control group (9.41±1.07) MPa, even more than those with sandblast(14.82±2.01) MPa (PUV and cold plasma treatment. The surface C/O ratio also decreased after UV and cold plasma treatment. Zirconia specimens treated with UV and cold plasma could significantly improve the hydrophilicity. The surface

Special Advanced Studies for Pollution Prevention. Delivery Order 0017: Sol-Gel Surface Preparation for Carbon Steel and Stainless Steel Bonding

National Research Council Canada - National Science Library

Zheng, Haixing

1997-01-01

The objective of this program is to study the feasibility of using sol-gel active alumina coatings for the surface preparation of carbon steel and stainless steel for adhesive bonding, and to optimize...

Pre-sintered Y-TZP sandblasting: effect on surface roughness, phase transformation, and Y-TZP/veneer bond strength

Directory of Open Access Journals (Sweden)

Carla Müller Ramos-Tonello

Full Text Available Abstract Sandblasting is a common method to try to improve the Y-TZP/veneer bond strength of dental prostheses, however, it may put stress on zirconia surfaces and could accelerate the t→m phase transformation. Y-TZP sandblasting before sintering could be an alternative to improve surface roughness and bonding strength of veneering ceramic. Objectives. The aim of this study was to analyze the effect of Y-TZP pre-sintering sandblasting on surface roughness, phase transformation, and the Y-TZP/veneer shear bond strength. Material and Methods. The Y-TZP specimen surface underwent sandblasting with aluminum oxide (50 μm pre-sintering (Z-PRE and post-sintering (Z-POS. Z-CTR was not subjected to surface treatment. After ceramic veneer application, the specimens were subjected to shear bond testing. Surface roughness was analyzed by confocal microscopy. Y-TZP monoclinic and tetragonal phases were evaluated by micro-Raman spectroscopy. Shear bond strength and surface roughness data were analyzed by One-way ANOVA and Tukey tests (α=0.05. Differences in the wave numbers and the broadening bands of the Raman spectra were compared among groups. Results. Z-POS (9.73±5.36 MPa and Z-PRE (7.94±2.52 MPa showed the highest bond strength, significantly higher than that of Z-CTR (5.54±2.14 MPa. The Ra of Z-PRE (1.59±0.23 µm was much greater and significantly different from that of Z-CTR (0.29±0.05 µm and Z-POS (0.77±0.13 µm. All groups showed bands typical of the tetragonal (T and monoclinic (M phases. Y-TZP sandblasting before sintering resulted in rougher surfaces but did not increase the shear bond strength compared to post-sintering and increased surface defects. Conclusions. Surface treatment with Al3O2, regardless of the moment and application, improves the results of Y-TZP/veneer bonding and is not a specific cause of t→m transformation.

Effects of surface treatment and artificial aging on the shear bond strength of orthodontic brackets bonded to four different provisional restorations.

Science.gov (United States)

Al Jabbari, Youssef S; Al Taweel, Sara M; Al Rifaiy, Mohammed; Alqahtani, Mohammed Q; Koutsoukis, Theodoros; Zinelis, Spiros

2014-07-01

To evaluate the combined effects of material type, surface treatment, and thermocycling on the bond strength of orthodontic brackets to materials used for the fabrication of provisional crowns. Four materials were included in this study (ProTemp, Trim Plus, Trim II, and Superpont C+B). Sixty cylindrical specimens (1 × 3 cm) were prepared from each material and equally divided into three groups. The first group was ground with silica carbide paper, the second was polished with pumice, and the last group was sandblasted with 50-µm aluminum oxide particles. Stainless-steel maxillary central incisor brackets (Victory Series, 3M) were bonded to the provisional material specimens with Transbond XT light-cured composite resin, and half of the specimens from each group were thermocycled 500 times in 5°C and 55°C water baths. Then the brackets were debonded with shear testing, and the results were statistically analyzed by three-way analysis of variance and Tukey's multiple-comparison tests at α  =  0.05. Adhesive Remnant Index (ARI) was also identified. Before and after thermocycling, ProTemp materials showed the highest shear bond strength with orthodontic brackets (10.3 and 13.1 MPa, respectively). The statistical analysis indicated an interaction among the three independent variables (P < .05) and statistically significant differences in bond strength among provisional materials (P < .001), surface treatments (P < .001), and thermocycling (P < .05). According to the ARI, most groups demonstrated adhesive failure. The provisional material type, surface treatment, and artificial aging have a significant effect on bond strength. Sandblasting treatment exerts a beneficial effect on shear bond strength.

Four chemical methods of porcelain conditioning and their influence over bond strength and surface integrity

Science.gov (United States)

Stella, João Paulo Fragomeni; Oliveira, Andrea Becker; Nojima, Lincoln Issamu; Marquezan, Mariana

2015-01-01

OBJECTIVE: To assess four different chemical surface conditioning methods for ceramic material before bracket bonding, and their impact on shear bond strength and surface integrity at debonding. METHODS: Four experimental groups (n = 13) were set up according to the ceramic conditioning method: G1 = 37% phosphoric acid etching followed by silane application; G2 = 37% liquid phosphoric acid etching, no rinsing, followed by silane application; G3 = 10% hydrofluoric acid etching alone; and G4 = 10% hydrofluoric acid etching followed by silane application. After surface conditioning, metal brackets were bonded to porcelain by means of the Transbond XP system (3M Unitek). Samples were submitted to shear bond strength tests in a universal testing machine and the surfaces were later assessed with a microscope under 8 X magnification. ANOVA/Tukey tests were performed to establish the difference between groups (α= 5%). RESULTS: The highest shear bond strength values were found in groups G3 and G4 (22.01 ± 2.15 MPa and 22.83 ± 3.32 Mpa, respectively), followed by G1 (16.42 ± 3.61 MPa) and G2 (9.29 ± 1.95 MPa). As regards surface evaluation after bracket debonding, the use of liquid phosphoric acid followed by silane application (G2) produced the least damage to porcelain. When hydrofluoric acid and silane were applied, the risk of ceramic fracture increased. CONCLUSIONS: Acceptable levels of bond strength for clinical use were reached by all methods tested; however, liquid phosphoric acid etching followed by silane application (G2) resulted in the least damage to the ceramic surface. PMID:26352845

Improved Interfacial Bonding in Magnesium/Aluminum Overcasting Systems by Aluminum Surface Treatments

Science.gov (United States)

Zhang, Hui; Chen, Yiqing; Luo, Alan A.

2014-12-01

"Overcasting" technique is used to produce bimetallic magnesium/aluminum (Mg/Al) structures where lightweight Mg can be cast onto solid Al substrates. An inherent difficulty in creating strong Mg/Al interfacial bonding is the natural oxide film on the solid Al surfaces, which reduces the wettability between molten Mg and Al substrates during the casting process. In the paper, an "electropolishing + anodizing" surface treatment has been developed to disrupt the oxide film on a dilute Al-0.08 wt pct Ga alloy, improving the metallurgical bonding between molten Mg and Al substrates in the bimetallic experiments carried out in a high-vacuum test apparatus. The test results provided valuable information of the interfacial phenomena of the Mg/Al bimetallic samples. The results show significantly improved metallurgical bonding in the bimetallic samples with "electropolishing + anodizing" surface treatment and Ga alloying. It is recommended to adjust the pre-heating temperature and time of the Al substrates and the Mg melt temperature to control the interfacial reactions for optimum interfacial properties in the actual overcasting processes.

Bonding of the Polymer Polyetheretherketone (PEEK) to Human Dentin: Effect of Surface Treatments.

Science.gov (United States)

Rocha, Regina Furbino Villefort; Anami, Lilian Costa; Campos, Tiago Moreira Bastos; Melo, Renata Marques de; Souza, Rodrigo Othávio de Assunção E; Bottino, Marco Antonio

2016-01-01

Polyetheretherketone (PEEK) is a material suitable for frameworks of fixed dental prostheses. The effect of different surface treatments on the bond strength of PEEK bonded to human dentin was evaluated. One hundred PEEK cylinders (3 mm×3 mm) were divided into five groups according to surface treatment: silica coating, sandblasting with 45 μm Al2O3 particles, etching with 98% sulfuric acid for 5, 30 and for 60 s. These cylinders were luted with resin cement onto 50 human molars. First, each tooth was embedded in epoxy resin and the buccal dentin surface was exposed. Then, two delimited dentin areas (Æ:3 mm) per tooth were etched with 35% phosphoric acid and bonded with a two-step self-priming adhesive system. After the luting procedure the specimens were stored in water (24 h/37 °C). Shear bond strength (SBS) was tested using a universal testing machine (crosshead speed 0.5 mm/min; load cell 50 kgf) and failure types were assessed. Stress data (MPa) were analyzed using the Kruskal-Wallis test. Comparison of the proportions of different failure types was performed using the Bonferroni method (pPEEK, resin cement and dentin.

THE EFFECT OF BONDING AND SURFACE SEALANT APPLICATION ON POSTOPERATIVE SENSITIVITY FROM POSTERIOR COMPOSITES

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Neslihan TEKÇE

2015-10-01

Full Text Available Purpose: The purpose of the study was to evaluate the postoperative sensitivity of posterior Class I composite restoration at short-term, restorated with two different all-in-one self-etch adhesives with or without surface sealant application. Materials and Methods: 44 restorations were inserted in 11 patients who required Class I restorations in their molars. Each patient received 4 restorations, thus four groups were formed; (1 G-Aenial Bond (GC, Japan; (2 Clearfil S3 Bond (Kuraray, Japan; (3 G-Aenial Bond+Fortify Plus (Bisco, USA, (4 Clearfil S3 Bond+Fortify Plus. Sensitivity was evaluated at 24h, 7, 15, and 30 days using cold air, ice, and pressure stimuli using a visual analog scale. Comparisons of continuous variables between the sensitivity evaluations were performed using the Friedman’s One-Way Analysis of Variance with repeated measures test (p0.05. The use of Clearfil S3 Bond resulted in almost the same level of postoperative sensitivity as did the use of G-Aenial Bond. The highest sensitivity scores were observed for the surface sealant applied teeth without any statistical significance (p>0.05. Conclusions: Self etch adhesives displayed postoperative sensitivity. The sensitivity scores slightly decreased at the end of 30 days (p>0.05. Surface sealant application did not result in a decrease in sensitivity scores for either dentin adhesives.

Evaluation of Surface Treatment Methods on the Bond Strength of Zirconia Ceramics Systems, Resin Cements and Tooth Surface

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Akkuş Emek

2015-07-01

Full Text Available Objectives: To compare the effects of airborne-particle abrasion (APA and tribochemical silica coating (TSC surface treatment methods on the shear bond strength of zirconia ceramics systems, resin cements and tooth surface

Rhodium-Catalyzed C-C Bond Formation via Heteroatom-Directed C-H Bond Activation

Energy Technology Data Exchange (ETDEWEB)

Colby, Denise; Bergman, Robert; Ellman, Jonathan

2010-05-13

Once considered the 'holy grail' of organometallic chemistry, synthetically useful reactions employing C-H bond activation have increasingly been developed and applied to natural product and drug synthesis over the past decade. The ubiquity and relative low cost of hydrocarbons makes C-H bond functionalization an attractive alternative to classical C-C bond forming reactions such as cross-coupling, which require organohalides and organometallic reagents. In addition to providing an atom economical alternative to standard cross - coupling strategies, C-H bond functionalization also reduces the production of toxic by-products, thereby contributing to the growing field of reactions with decreased environmental impact. In the area of C-C bond forming reactions that proceed via a C-H activation mechanism, rhodium catalysts stand out for their functional group tolerance and wide range of synthetic utility. Over the course of the last decade, many Rh-catalyzed methods for heteroatom-directed C-H bond functionalization have been reported and will be the focus of this review. Material appearing in the literature prior to 2001 has been reviewed previously and will only be introduced as background when necessary. The synthesis of complex molecules from relatively simple precursors has long been a goal for many organic chemists. The ability to selectively functionalize a molecule with minimal pre-activation can streamline syntheses and expand the opportunities to explore the utility of complex molecules in areas ranging from the pharmaceutical industry to materials science. Indeed, the issue of selectivity is paramount in the development of all C-H bond functionalization methods. Several groups have developed elegant approaches towards achieving selectivity in molecules that possess many sterically and electronically similar C-H bonds. Many of these approaches are discussed in detail in the accompanying articles in this special issue of Chemical Reviews. One approach

Origin of the Ability of α-Fe2 O3 Mesopores to Activate C-H Bonds in Methane.

Science.gov (United States)

Dong, Bing; Han, Zhen; Zhang, Yongbo; Yu, Youyi; Kong, Aiguo; Shan, Yongkui

2016-02-01

Methane is a most abundant and inexpensive hydrocarbon feedstock for the production of chemicals and fuels. However, it is extremely difficult to directly convert methane to higher hydrocarbons because the C-H bonds in methane are the most stable C-H bonds of all hydrocarbons. The activation of the C-H bonds in methane by using an efficient and mild route remains a daunting challenge. Here, we show that the inner surface structures of the pore walls in mesoporous α-Fe 2 O 3 possess excellent catalytic performance for methane activation and convert C-H bonds into the C-O bonds in an O 2 atmosphere at 140 °C. We found that such unusual structures are mainly comprised of turbostratic ribbons and K crystal faces and have higher catalytic activity than the (110) plane. These results are without precedent in the history of catalysis chemistry and will provide a new pathway for designing and preparing highly efficient catalytic materials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Redox-​Active Ligand-​Induced Homolytic Bond Activation

NARCIS (Netherlands)

Broere, D.L.J.; Metz, L.L.; de Bruin, B.; Reek, J.N.H.; Siegler, M.A.; van der Vlugt, J.I.

2015-01-01

Coordination of the novel redox-​active phosphine-​appended aminophenol pincer ligand (PNOH2) to PdII generates a paramagnetic complex with a persistent ligand-​centered radical. The complex undergoes fully reversible single-​electron oxidn. and redn. Homolytic bond activation of diphenyldisulfide

In situ metalation of free base phthalocyanine covalently bonded to silicon surfaces

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Fabio Lupo

2014-11-01

Full Text Available Free 4-undecenoxyphthalocyanine molecules were covalently bonded to Si(100 and porous silicon through thermic hydrosilylation of the terminal double bonds of the undecenyl chains. The success of the anchoring strategy on both surfaces was demonstrated by the combination of X-ray photoelectron spectroscopy with control experiments performed adopting the commercially available 2,3,9,10,16,17,23,24-octakis(octyloxy-29H,31H-phthalocyanine, which is not suited for silicon anchoring. Moreover, the study of the shape of the XPS N 1s band gave relevant information on the interactions occurring between the anchored molecules and the substrates. The spectra suggest that the phthalocyanine ring interacts significantly with the flat Si surface, whilst ring–surface interactions are less relevant on porous Si. The surface-bonded molecules were then metalated in situ with Co by using wet chemistry. The efficiency of the metalation process was evaluated by XPS measurements and, in particular, on porous silicon, the complexation of cobalt was confirmed by the disappearance in the FTIR spectra of the band at 3290 cm−1 due to –NH stretches. Finally, XPS results revealed that the different surface–phthalocyanine interactions observed for flat and porous substrates affect the efficiency of the in situ metalation process.

Effect of Various Treatment Modalities on Surface Characteristics and Shear Bond Strengths of Polyetheretherketone-Based Core Materials.

Science.gov (United States)

Çulhaoğlu, Ahmet Kürşat; Özkır, Serhat Emre; Şahin, Volkan; Yılmaz, Burak; Kılıçarslan, Mehmet Ali

2017-11-13

To investigate the effect of different surface treatments on the surface roughness (Ra), wettability, and shear bond strength of polyetheretherketone (PEEK) to composite resin. One hundred ninety eight PEEK specimens were divided into six groups (n = 33). Specimen surfaces were treated with the following surface treatment modalities: silicoating (CoJet), acetone treatment, acid etching (H 2 SO 4 ), airborne particle abrasion (Al 2 O 3 ), laser irradiation (Yb:PL laser), and the nontreated surface serving as the control. Surface roughness was measured with an profilometer (n = 11) and a goniometer was used to measure the surface wettability through contact angle (θ)(n = 11). PEEK surfaces were veneered with a composite resin (n = 11). The specimens were then thermocycled for 10,000 cycles at 5 to 55°C. Shear bond strengths between the PEEK and composite resin were measured with an universal test machine. One-way ANOVA was used to analyze the data. Tukey's post-hoc test was used to determine significant differences between groups (α = 0.05). Surface roughness and wettability of PEEK surfaces along with shear bond strength of PEEK to composite resin were influenced by the surface treatments. (p PEEK surfaces treated by laser irradiation (2.85 ± 0.2 µm) followed by airborne particle abrasion (2.26 ± 0.33 µm), whereas other surface treatment modalities provided similar Ra values, with the acid-etched PEEK surfaces having the lowest mean Ra values (0.35 ± 0.14 µm). Silicoating provided the most wettable PEEK surfaces (48.04 ± 6.28º), followed by either acetone treatment (70.19 ± 4.49º) or acid treatment (76.07 ± 6.61º). Decreased wettability was observed for airborne particle abraded (84.83 ± 4.56º) and laser-treated PEEK surfaces (103.06 ± 4.88º). The highest mean shear bond strength values were observed for acid-etched PEEK surfaces (15.82 ± 4.23 MPa) followed by laser irradiated (11.46 ± 1.97 MPa), airborne particle abraded (10.81 ± 3.06 MPa

Repair bond strength of composite resin to sandblasted and laser irradiated Y-TZP ceramic surfaces.

Science.gov (United States)

Kirmali, Omer; Barutcigil, Çağatay; Ozarslan, Mehmet Mustafa; Barutcigil, Kubilay; Harorlı, Osman Tolga

2015-01-01

This study investigated the effects of different surface treatments on the repair bond strength of yttrium-stabilized tetragonal zirconia polycrystalline ceramic (Y-TZP) zirconia to a composite resin. Sixty Y-TZP zirconia specimens were prepared and randomly divided into six groups (n = 10) as follows: Group 1, surface grinding with Cimara grinding bur (control); Group 2, sandblasted with 30 µm silica-coated alumina particles; Group 3, Nd:YAG laser irradiation; Group 4, Er,Cr:YSGG laser irradiation; Group 5, sandblasted + Nd:YAG laser irradiation; and Group 6, sandblasted + Er,Cr:YSGG laser irradiation. After surface treatments, the Cimara(®) System was selected for the repair method and applied to all specimens. A composite resin was built-up on each zirconia surface using a cylindrical mold (5 × 3 mm) and incrementally filled. The repair bond strength was measured with a universal test machine. Data were analyzed using a one-way ANOVA and a Tukey HSD test (p = 0.05). Surface topography after treatments were evaluated by a scanning electron microscope (SEM). Shear bond strength mean values ranged from 15.896 to 18.875 MPa. There was a statistically significant difference between group 3 and the control group (p < 0.05). Also, a significant increase in bond strength values was noted in group 6 (p < 0.05). All surface treatment methods enhanced the repair bond strength of the composite to zirconia; however, there were no significant differences between treatment methods. The results revealed that Nd:YAG laser irradiation along with the combination of sandblasting and Er,Cr:YSGG laser irradiation provided a significant increase in bond strength between the zirconia and composite resin. © Wiley Periodicals, Inc.

Bonding of Metal Orthodontic Attachments to Sandblasted Porcelain and Zirconia Surfaces

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Amitoj S. Mehta

2016-01-01

Full Text Available This study evaluates tensile bond strength (TBS of metal orthodontic attachments to sandblasted feldspathic porcelain and zirconia with various bonding protocols. Thirty-six (36 feldspathic and 36 zirconia disc samples were prepared, glazed, embedded in acrylic blocks and sandblasted, and divided into three groups according to one or more of the following treatments: hydrofluoric acid 4% (HF, Porcelain Conditioner silane primer, Reliance Assure® primer, Reliance Assure plus® primer, and Z Prime™ plus zirconia primer. A round traction hook was bonded to each sample. Static tensile bond strength tests were performed in a universal testing machine and adhesive remnant index (ARI scoring was done using a digital camera. One-way ANOVA and Pearson chi-square tests were used to analyze TBS (MPa and ARI scores. No statistically significant mean differences were found in TBS among the different bonding protocols for feldspathic and zirconia, p values = 0.369 and 0.944, respectively. No statistically significant distribution of ARI scores was found among the levels of feldspathic, p value = 0.569. However, statistically significant distribution of ARI scores was found among the levels of zirconia, p value = 0.026. The study concluded that silanization following sandblasting resulted in tensile bond strengths comparable to other bonding protocols for feldspathic and zirconia surface.

Toward accurate prediction of potential energy surfaces and the spectral density of hydrogen bonded systems

International Nuclear Information System (INIS)

Rekik, Najeh

2014-01-01

Despite the considerable progress made in quantum theory and computational methods, detailed descriptions of the potential energy surfaces of hydrogen-bonded systems have not yet been achieved. In addition, the hydrogen bond (H-bond) itself is still so poorly understood at the fundamental level that it remains unclear exactly what geometry constitutes a “real” H-bond. Therefore, in order to investigate features essential for hydrogen bonded complexes, a simple, efficient, and general method for calculating matrix elements of vibrational operators capable of describing the stretching modes and the H-bond bridges of hydrogen-bonded systems is proposed. The derived matrix elements are simple and computationally easy to evaluate, which makes the method suitable for vibrational studies of multiple-well potentials. The method is illustrated by obtaining potential energy surfaces for a number of two-dimensional systems with repulsive potentials chosen to be in Gaussian form for the stretching mode and of the Morse-type for the H-bond bridge dynamics. The forms of potential energy surfaces of weak and strong hydrogen bonds are analyzed by varying the asymmetry of the Gaussian potential. Moreover, the choice and applicability of the selected potential for the stretching mode and comparison with other potentials used in the area of hydrogen bond research are discussed. The approach for the determination of spectral density has been constructed in the framework of the linear response theory for which spectral density is obtained by Fourier transform of the autocorrelation function of the dipole moment operator of the fast mode. The approach involves anharmonic coupling between the high frequency stretching vibration (double well potential) and low-frequency donor-acceptor stretching mode (Morse potential) as well as the electrical anharmonicity of the dipole moment operator of the fast mode. A direct relaxation mechanism is incorporated through a time decaying exponential

Effect of LASER Irradiation on the Shear Bond Strength of Zirconia Ceramic Surface to Dentin

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Sima Shahabi

2012-09-01

Full Text Available Background and Aims: Reliable bonding between tooth substrate and zirconia-based ceramic restorations is always of great importance. The laser might be useful for treatment of ceramic surfaces. The aim of the present study was to investigate the effect of laser irradiation on the shear bond strength of zirconia ceramic surface to dentin. Materials and Methods: In this experimental in vitro study, 40 Cercon zirconia ceramic blocks were fabricated. The surface treatment was performed using sandblasting with 50-micrometer Al2O3, CO2 laser, or Nd:YAG laser in each test groups. After that, the specimens were cemented to human dentin with resin cement. The shear bond strength of ceramics to dentin was determined and failure mode of each specimen was analyzed by stereo-microscope and SEM investigations. The data were statistically analyzed by one-way analysis of variance and Tukey multiple comparisons. The surface morphology of one specimen from each group was investigated under SEM. Results: The mean shear bond strength of zirconia ceramic to dentin was 7.79±3.03, 9.85±4.69, 14.92±4.48 MPa for CO2 irradiated, Nd:YAG irradiated, and sandblasted specimens, respectively. Significant differences were noted between CO2 (P=0.001 and Nd:YAG laser (P=0.017 irradiated specimens with sandblasted specimens. No significant differences were observed between two laser methods (P=0.47. The mode of bond failure was predominantly adhesive in test groups (CO2 irradiated specimens: 75%, Nd:YAG irradiated: 66.7%, and sandblasting: 41.7%. Conclusion: Under the limitations of the present study, surface treatment of zirconia ceramics using CO2 and Nd:YAG lasers was not able to produce adequate bond strength with dentin surfaces in comparison to sandblasting technique. Therefore, the use of lasers with the mentioned parameters may not be recommended for the surface treatment of Cercon ceramics.

Removal of dangling bonds and surface states on silicon (001) with a monolayer of selenium

International Nuclear Information System (INIS)

Tao Meng; Udeshi, Darshak; Basit, Nasir; Maldonado, Eduardo; Kirk, Wiley P.

2003-01-01

Dangling bonds and surface states are inherent to semiconductor surfaces. By passivating dangling bonds on the silicon (001) surface with a monolayer of selenium, surface states are removed from the band gap. Magnesium contacts on selenium-passivated silicon (001) behave ohmically, as expected from the work function of magnesium and the electron affinity of silicon. After rapid thermal annealing and hot-plate annealing, magnesium contacts on selenium-passivated silicon (001) show better thermal stability than on hydrogen-passivated silicon (001), which is attributed to the suppression of silicide formation by selenium passivation

Dimensional accuracy and surface property of titanium casting using gypsum-bonded alumina investment.

Science.gov (United States)

Yan, Min; Takahashi, Hidekazu; Nishimura, Fumio

2004-12-01

The aim of the present study was to evaluate the dimensional accuracy and surface property of titanium casting obtained using a gypsum-bonded alumina investment. The experimental gypsum-bonded alumina investment with 20 mass% gypsum content mixed with 2 mass% potassium sulfate was used for five cp titanium castings and three Cu-Zn alloy castings. The accuracy, surface roughness (Ra), and reaction layer thickness of these castings were investigated. The accuracy of the castings obtained from the experimental investment ranged from -0.04 to 0.23%, while surface roughness (Ra) ranged from 7.6 to 10.3microm. A reaction layer of about 150 microm thickness under the titanium casting surface was observed. These results suggested that the titanium casting obtained using the experimental investment was acceptable. Although the reaction layer was thin, surface roughness should be improved.

Bonding techniques for hybrid active pixel sensors (HAPS)

Energy Technology Data Exchange (ETDEWEB)

Bigas, M. [Centre Nacional de Microelectronica, CNM-IMB (CSIC), Campus Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona (Spain)]. E-mail: Marc.Bigas@cnm.es; Cabruja, E. [Centre Nacional de Microelectronica, CNM-IMB (CSIC), Campus Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona (Spain)]. E-mail: Enric.Cabruja@cnm.es; Lozano, M. [Centre Nacional de Microelectronica, CNM-IMB (CSIC), Campus Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona (Spain)

2007-05-01

A hybrid active pixel sensor (HAPS) consists of an array of sensing elements which is connected to an electronic read-out unit. The most used way to connect these two different devices is bump bonding. This interconnection technique is very suitable for these systems because it allows a very fine pitch and a high number of I/Os. However, there are other interconnection techniques available such as direct bonding. This paper, as a continuation of a review [M. Lozano, E. Cabruja, A. Collado, J. Santander, M. Ullan, Nucl. Instr. and Meth. A 473 (1-2) (2001) 95-101] published in 2001, presents an update of the different advanced bonding techniques available for manufacturing a hybrid active pixel detector.

Friedel-Crafts reaction of benzyl fluorides: selective activation of C-F bonds as enabled by hydrogen bonding.

Science.gov (United States)

Champagne, Pier Alexandre; Benhassine, Yasmine; Desroches, Justine; Paquin, Jean-François

2014-12-08

A Friedel-Crafts benzylation of arenes with benzyl fluorides has been developed. The reaction produces 1,1-diaryl alkanes in good yield under mild conditions without the need for a transition metal or a strong Lewis acid. A mechanism involving activation of the C-F bond through hydrogen bonding is proposed. This mode of activation enables the selective reaction of benzylic C-F bonds in the presence of other benzylic leaving groups. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Verification of the effect of surface preparation on Hot Isostatic Pressing diffusion bonding joints of CLAM steel

Energy Technology Data Exchange (ETDEWEB)

Zhao, Yanyun [University of Science and Technology of China, Hefei, Anhui 230027 (China); Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); Li, Chunjing, E-mail: chunjing.li@fds.org.cn [Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); Huang, Bo; Liu, Shaojun [Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); Huang, Qunying [University of Science and Technology of China, Hefei, Anhui 230027 (China); Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei, Anhui 230031 (China)

2014-12-15

Hot Isostatic Pressing (HIP) diffusion bonding with CLAM steel is the primary candidate fabrication technique for the first wall (FW) of DFLL-TBM. Surface state is one of the key factors for the joints quality. The effect of surface state prepared with grinder and miller on HIP diffusion bonding joints of CLAM steel was investigated. HIP diffusion bonding was performed at 140 MPa and 1373 K within 3 h. The mechanical properties of the joints were investigated with instrumented Charpy V-notch impact tests and the microstructures of the joints were analyzed with scanning electron microscopy (SEM). The results showed that the milled samples with fine surface roughness were more suitable for CLAM steel HIP diffusion bonding.

Active application of primer acid on acid-treated enamel: Influence on the bond effectiveness of self-etch adhesives systems.

Science.gov (United States)

Araújo, Cíntia Tereza Pimenta; Prieto, Lúcia Trazzi; Costa, Daiane Cristianismo; Bosso, Mariana Avalone; Coppini, Erick Kamiya; Dias, Carlos Tadeu Santos; Paulillo, Luis Alexandre Maffei Sartini

2017-08-01

Evaluate the composite-to-enamel bond after passive or active application of self-etching primer systems on polished or pre-etched enamel with phosphoric acid. Two self-etch adhesives systems (SEAS) were used: Clearfil SE Bond and Easy Bond. Third human molars were divided into 8 groups (N = 10). The crown of each tooth was sectioned into halves and the mesial/distal surfaces were used. The adhesives were actively or passively applied on enamel with or without prior phosphoric-acid etching. Resin composite cylinders were built after adhesive application. After stored in relative humidity for 24 hr/37°C the specimens were subjected to microshear test in universal testing a machine at a crosshead speed of 0.5 mm/minute. The results were analyzed with three-way ANOVA and the Tukey test. The enamel-etching pattern was evaluated under SEM. The 2-step SEAS system presented significantly higher adhesive bond strength means (47.37 MPa) than the 1-step (36.87 MPa). A poor enamel- etching pattern was observed in active mode showing irregular and short resin tags, however there was not compromised the bond strength. Active or passive application produced similar values of bond strength to enamel regardless of enamel pretreatment and type of SEAS. © 2017 Wiley Periodicals, Inc.

Direct synthesis of sp-bonded carbon chains on graphite surface by femtosecond laser irradiation

International Nuclear Information System (INIS)

Hu, A.; Rybachuk, M.; Lu, Q.-B.; Duley, W. W.

2007-01-01

Microscopic phase transformation from graphite to sp-bonded carbon chains (carbyne) and nanodiamond has been induced by femtosecond laser pulses on graphite surface. UV/surface enhanced Raman scattering spectra and x-ray photoelectron spectra displayed the local synthesis of carbyne in the melt zone while nanocrystalline diamond and trans-polyacetylene chains form in the edge area of gentle ablation. These results evidence possible direct 'writing' of variable chemical bonded carbons by femtosecond laser pulses for carbon-based applications

Water's Interfacial Hydrogen Bonding Structure Reveals the Effective Strength of Surface-Water Interactions.

Science.gov (United States)

Shin, Sucheol; Willard, Adam P

2018-06-05

We combine all-atom molecular dynamics simulations with a mean field model of interfacial hydrogen bonding to analyze the effect of surface-water interactions on the structural and energetic properties of the liquid water interface. We show that the molecular structure of water at a weakly interacting ( i.e., hydrophobic) surface is resistant to change unless the strength of surface-water interactions are above a certain threshold. We find that below this threshold water's interfacial structure is homogeneous and insensitive to the details of the disordered surface, however, above this threshold water's interfacial structure is heterogeneous. Despite this heterogeneity, we demonstrate that the equilibrium distribution of molecular orientations can be used to quantify the energetic component of the surface-water interactions that contribute specifically to modifying the interfacial hydrogen bonding network. We identify this specific energetic component as a new measure of hydrophilicity, which we refer to as the intrinsic hydropathy.

A novel disulfide bond in the SH2 Domain of the C-terminal Src kinase controls catalytic activity.

Science.gov (United States)

Mills, Jamie E; Whitford, Paul C; Shaffer, Jennifer; Onuchic, Jose N; Adams, Joseph A; Jennings, Patricia A

2007-02-02

The SH2 domain of the C-terminal Src kinase [Csk] contains a unique disulfide bond that is not present in other known SH2 domains. To investigate whether this unusual disulfide bond serves a novel function, the effects of disulfide bond formation on catalytic activity of the full-length protein and on the structure of the SH2 domain were investigated. The kinase activity of full-length Csk decreases by an order of magnitude upon formation of the disulfide bond in the distal SH2 domain. NMR spectra of the fully oxidized and fully reduced SH2 domains exhibit similar chemical shift patterns and are indicative of similar, well-defined tertiary structures. The solvent-accessible disulfide bond in the isolated SH2 domain is highly stable and far from the small lobe of the kinase domain. However, reduction of this bond results in chemical shift changes of resonances that map to a cluster of residues that extend from the disulfide bond across the molecule to a surface that is in direct contact with the small lobe of the kinase domain in the intact molecule. Normal mode analyses and molecular dynamics calculations suggest that disulfide bond formation has large effects on residues within the kinase domain, most notably within the active-site cleft. Overall, the data indicate that reversible cross-linking of two cysteine residues in the SH2 domain greatly impacts catalytic function and interdomain communication in Csk.

Immediate repair bond strengths of microhybrid, nanohybrid and nanofilled composites after different surface treatments

NARCIS (Netherlands)

Rinastiti, Margareta; Siswomihardjo, Widowati; Busscher, Henk J.; Ozcan, Mutlu

Objectives: To evaluate immediate repair bond strengths and failure types of resin composites with and without surface conditioning and characterize the interacting composite surfaces by their surface composition and roughness. Methods: Microhybrid, nanohybrid and nanofilled resin composites were

Detailed analysis of surface asperity deformation mechanism in diffusion bonding of steel hollow structural components

Energy Technology Data Exchange (ETDEWEB)

Zhang, C. [School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072 (China); Laboratoire de Mecanique des Contacts et des Structures (LaMCoS), INSA Lyon, 20 Avenue des Sciences, F-69621 Villeurbanne Cedex (France); Li, H. [School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072 (China); Li, M.Q., E-mail: zc9997242256@126.com [School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072 (China)

2016-05-15

Graphical abstract: This study focused on the detailed analysis of surface asperity deformation mechanism in diffusion bonding of steel hollow structural component. A special surface with regular patterns was processed to be joined so as to observe the extent of surface asperity deformation under different applied bonding pressures. Fracture surface characteristic combined with surface roughness profiles distinctly revealed the enhanced surface asperity deformation as the applied pressure increases. The influence of surface asperity deformation mechanism on joint formation was analyzed: (a) surface asperity deformation not only directly expanded the interfacial contact areas, but also released deformation heat and caused defects, indirectly accelerating atomic diffusion, then benefits to void shrinkage; (b) surface asperity deformation readily introduced stored energy difference between two opposite sides of interface grain boundary, resulting in strain induced interface grain boundary migration. In addition, the influence of void on interface grain boundary migration was analyzed in detail. - Highlights: • A high quality hollow structural component has been fabricated by diffusion bonding. • Surface asperity deformation not only expands the interfacial contact areas, but also causes deformation heat and defects to improve the atomic diffusion. • Surface asperity deformation introduces the stored energy difference between the two opposite sides of interface grain boundary, leading to strain induced interface grain boundary migration. • The void exerts a dragging force on the interface grain boundary to retard or stop interface grain boundary migration. - Abstract: This study focused on the detailed analysis of surface asperity deformation mechanism in similar diffusion bonding as well as on the fabrication of high quality martensitic stainless steel hollow structural components. A special surface with regular patterns was processed to be joined so as to

Surface properties and bond strength measurements of N-vinylcaprolactam (NVC)-containing glass-ionomer cements.

Science.gov (United States)

Moshaverinia, Alireza; Chee, Winston W; Brantley, William A; Schricker, Scott R

2011-03-01

N-vinylcaprolactam (NVC)-containing glass ionomers are promising dental restorative materials with improved mechanical properties; however, little information is available on other physical characteristics of these types of modified glass ionomers, especially their surface properties. Understanding the surface characteristics and behavior of glass ionomers is important for understanding their clinical behavior and predictability as dental restorative materials. The purpose of this study was to investigate the effect of NVC-containing terpolymers on the surface properties and bond strength to dentin of GIC (glass-ionomer cement), and to evaluate the effect of NVC-containing terpolymer as a dentin conditioner. The terpolymer of acrylic acid (AA)-itaconic acid (IA)-N-vinylcaprolactam (NVC) with a molar ratio of 8:1:1 (AA:IA:NVC) was synthesized by free radical polymerization and characterized using nuclear magnetic resonance ((1)H-NMR) and Fourier transform infrared spectroscopy (FTIR). The synthesized terpolymer was used in glass-ionomer cement formulations (Fuji IX GP). Ten disc-shaped specimens (12 × 1 mm) were mixed and fabricated at room temperature. Surface properties (wettability) of modified cements were studied by contact angle measurements as a function of time. Work of adhesion values of different surfaces were also determined. The effect of NVC-modified polyacid on the bond strength of glass-ionomer cement to dentin was investigated. The mean data obtained from contact angle and bonding strength measurements were subjected to t test and 2-way ANOVA (α=.05). NVC-modified glass-ionomer cements showed significantly (Pcement also showed significantly higher values for shear bond strength to dentin (8.7 ±0.15 MPa after 1 month) when compared to the control group (8.4 ±0.13 MPa after 1 month). NVC-containing terpolymers may enhance the surface properties of GICs and increase their bond strength to the dentin. Furthermore, NVC-containing polyelectrolytes are

Enabling nucleophilic substitution reactions of activated alkyl fluorides through hydrogen bonding.

Science.gov (United States)

Champagne, Pier Alexandre; Pomarole, Julien; Thérien, Marie-Ève; Benhassine, Yasmine; Beaulieu, Samuel; Legault, Claude Y; Paquin, Jean-François

2013-05-03

It was discovered that the presence of water as a cosolvent enables the reaction of activated alkyl fluorides for bimolecular nucleophilic substitution reactions. DFT calculations show that activation proceeds through stabilization of the transition structure by a stronger F···H2O interaction and diminishing C-F bond elongation, and not simple transition state electrostatic stabilization. Overall, the findings put forward a distinct strategy for C-F bond activation through H-bonding.

Ultraclean Si/Si interface formation by surface preparation and direct bonding in ultrahigh vacuum

DEFF Research Database (Denmark)

Hermansson, Karin; Grey, Francois; Bengtsson, Stefan

1998-01-01

Silicon surfaces have been cleaned and bonded in ultrahigh vacuum, at a pressure in the 10(-10) Torr range. The bonded interfaces show extremely low contamination levels as measured by secondary ion mass spectroscopy. Nevertheless, a potential barrier could be detected at the interface by spreading...

The mystery of gold's chemical activity: local bonding, morphology and reactivity of atomic oxygen.

Science.gov (United States)

Baker, Thomas A; Liu, Xiaoying; Friend, Cynthia M

2011-01-07

Recently, gold has been intensely studied as a catalyst for key synthetic reactions. Gold is an attractive catalyst because, surprisingly, it is highly active and very selective for partial oxidation processes suggesting promise for energy-efficient "green" chemistry. The underlying origin of the high activity of Au is a controversial subject since metallic gold is commonly thought to be inert. Herein, we establish that one origin of the high activity for gold catalysis is the extremely reactive nature of atomic oxygen bound in 3-fold coordination sites on metallic gold. This is the predominant form of O at low concentrations on the surface, which is a strong indication that it is most relevant to catalytic conditions. Atomic oxygen bound to metallic Au in 3-fold sites has high activity for CO oxidation, oxidation of olefins, and oxidative transformations of alcohols and amines. Among the factors identified as important in Au-O interaction are the morphology of the surface, the local binding site of oxygen, and the degree of order of the oxygen overlayer. In this Perspective, we present an overview of both theory and experiments that identify the reactive forms of O and their associated charge density distributions and bond strengths. We also analyze and model the release of Au atoms induced by O binding to the surface. This rough surface also has the potential for O(2) dissociation, which is a critical step if Au is to be activated catalytically. We further show the strong parallels between product distributions and reactivity for O-covered Au at low pressure (ultrahigh vacuum) and for nanoporous Au catalysts operating at atmospheric pressure as evidence that atomic O is the active species under working catalytic conditions when metallic Au is present. We briefly discuss the possible contributions of oxidants that may contain intact O-O bonds and of the Au-metal oxide support interface in Au catalysis. Finally, the challenges and future directions for fully

Light Makes a Surface Banana-Bond Split: Photodesorption of Molecular Hydrogen from RuO ₂ (110)

Energy Technology Data Exchange (ETDEWEB)

Henderson, Michael A.; Mu, Rentao; Dahal, Arjun; Lyubinetsky, Igor; Dohnálek, Zdenek; Glezakou, Vassiliki-Alexandra; Rousseau, Roger

2016-07-20

The coordination of H2 to a metal center via polarization of its bond electron density, known as a Kubas complex, is the means by which H2 chemisorbs at Ru4+ sites on the rutile RuO2(110) surface. This distortion of electron density off an interatomic axis is often described as a ‘banana-bond.’ We show that the Ru-H2 banana-bond can be destabilized, and split, using visible light. Photodesorption of H2 (or D2) is evident by mass spectrometry and scanning tunneling microscopy. From time-dependent density functional theory, the key optical excitation splitting the Ru-H2 banana-bond involves an interband transition in RuO2 which effectively diminishes its Lewis acidity, and thereby weakening the Kubas complex. Such excitations are not expected to affect adsorbates on RuO2 given its metallic properties. Therefore, this common thermal co-catalyst employed in promoting water splitting is, itself, photo-active in the visible.

Quantification of the selective activation of C--H bonds in short chain alkanes: The reactivity of ethane, propane, isobutane, n-butane, and neopentane on Ir(111)

International Nuclear Information System (INIS)

Johnson, D.F.; Weinberg, W.H.

1995-01-01

The initial probabilities of precursor-mediated, dissociative chemisorption of the saturated hydrocarbons 13 C-labeled ethane, propane, isobutane, n-butane, and neopentane on the close-packed Ir(111) surface have been measured. The selective activation of primary (1 degree), secondary (2 degree), and tertiary (3 degree) C--H bonds has been quantified by examining the reactivities of the selectively deuterated isotopomers of propane, C 3 H 8 , CH 3 CD 2 CH 3 , and C 3 D 8 , and of isobutane, (CH 3 ) 3 CH, (CH 3 ) 3 CD, and (CD 3 ) 3 CH. With respect to the bottom of the physically adsorbed well for each hydrocarbon, the apparent C--H bond activation energies have been found to be 10.4±0.3 kcal/mol (ethane), 11.4±0.3 kcal/mol (propane), 11.5±0.3 kcal/mol (n-butane), 11.3±0.3 kcal/mol (i-butane), and 11.3±0.3 kcal/mol (neopentane). For all the alkanes examined, the ratios of the preexponential factors of the rate coefficients of reaction and desorption are 1x10 -2 . The C--D bond activation energies are higher than the corresponding C--H bond activation energies by 480 cal/mol (ethane), 630 cal/mol (propane), and 660 cal/mol (i-butane). By analyzing the primary kinetic isotope effects for the selectively deuterated isotopomers of propane and isobutane, the 2 degree C--H bond activation energy is found to be 310±160 cal/mol less than the 1 degree C--H bond activation energy on this surface, and similarly, 3 degree C--H bond cleavage is less by 80±70 cal/mol. The quantification of the branching ratios within the C--H bond activation channel for propane and isobutane on this surface shows that the formation of 1 degree-alkyl intermediates is, in general, favored over the formation of either 2 degree- or 3 degree-alkyl intermediates. (Abstract Truncated)

Effect of nonthermal plasma treatment on surface chemistry of commercially-pure titanium and shear bond strength to autopolymerizing acrylic resin

Energy Technology Data Exchange (ETDEWEB)

Vechiato-Filho, Aljomar José, E-mail: aljomarvechiatoflo@gmail.com [Department of Dental Materials and Prosthodontics, Aracatuba Dental School, Univ. Estadual Paulista — UNESP, Aracatuba, Sao Paulo (Brazil); Silva Vieira Marques, Isabella da [Department of Prosthodontics and Periodontology, Piracicaba Dental School, University of Campinas (UNICAMP), Piracicaba, Sao Paulo (Brazil); Santos, Daniela Micheline dos [Department of Dental Materials and Prosthodontics, Aracatuba Dental School, Univ. Estadual Paulista — UNESP, Aracatuba, Sao Paulo (Brazil); Oliveira Matos, Adaias [Department of Prosthodontics and Periodontology, Piracicaba Dental School, University of Campinas (UNICAMP), Piracicaba, Sao Paulo (Brazil); Rangel, Elidiane Cipriano; Cruz, Nilson Cristino da [Laboratory of Technological Plasmas (LaPTec), Engineering College, Univ. Estadual Paulista — UNESP, Sorocaba, Sao Paulo (Brazil); Barão, Valentim Adelino Ricardo [Department of Prosthodontics and Periodontology, Piracicaba Dental School, University of Campinas (UNICAMP), Piracicaba, Sao Paulo (Brazil)

2016-03-01

The effect of nonthermal plasma on the surface characteristics of commercially pure titanium (cp-Ti), and on the shear bond strength between an autopolymerizing acrylic resin and cp-Ti was investigated. A total of 96 discs of cp-Ti were distributed into four groups (n = 24): Po (no surface treatment), SB (sandblasting), Po + NTP and SB + NTP (methane plasma). Surface characterization was performed through surface energy, surface roughness, scanning microscopy, energy dispersive spectroscopy, and X-ray diffraction tests. Shear bond strength test was conducted immediately and after thermocycling. Surface treatment affected the surface energy and roughness of cp-Ti discs (P < .001). SEM–EDS showed the presence of the carbide thin film. XRD spectra revealed no crystalline phase changes. The SB + NTP group showed the highest bond strength values (6.76 ± 0.70 MPa). Thermocycling reduced the bond strength of the acrylic resin/cp-Ti interface (P < .05), except for Po group. NTP is an effective treatment option for improving the shear bond strength between both materials. - Highlights: • We tested the bond strength between two widely used materials in dentistry (acrylic and titanium). • We performed an innovative surface treatment with nonthermal plasma. • Increasing adhesion will avoid complications of full-arch implant-retained prostheses.

Breastfeeding and Active Bonding Protects against Children’s Internalizing Behavior Problems

Directory of Open Access Journals (Sweden)

Jianghong Liu

2013-12-01

Full Text Available Breastfeeding is associated with numerous health benefits to offspring and mothers and may improve maternal-infant bonding. Ample evidence suggests breastfeeding can improve child neurodevelopment, but more research is needed to establish whether breastfeeding is linked to the development of child psychopathology. This paper aims to explore the effects of both breastfeeding and mother-child interactions on child behavioral outcomes at a later age. Children from the China Jintan Child Cohort Study (N = 1267, at age six years old were assessed, along with their parents. Children who were breastfed exclusively for a period of time in the presence of active bonding were compared to those who were breastfed in the absence of active bonding as well as to children who were not exclusively breastfed, with or without active bonding. Results from ANOVA and GLM, using SPSS20, indicate that children who were breastfed and whose mothers actively engaged with them displayed the lowest risk of internalizing problems (mean = 10.01, SD = 7.21, while those who were neither exclusively breastfed nor exposed to active bonding had the least protection against later internalizing problems (mean = 12.79, SD = 8.14. The effect of breastfeeding on internalizing pathology likely represents a biosocial and holistic effect of physiological, and nutritive, and maternal-infant bonding benefits.

Influence of temporary cement contamination on the surface free energy and dentine bond strength of self-adhesive cements.

Science.gov (United States)

Takimoto, Masayuki; Ishii, Ryo; Iino, Masayoshi; Shimizu, Yusuke; Tsujimoto, Akimasa; Takamizawa, Toshiki; Ando, Susumu; Miyazaki, Masashi

2012-02-01

The surface free energy and dentine bond strength of self-adhesive cements were examined after the removal of temporary cements. The labial dentine surfaces of bovine mandibular incisors were wet ground with #600-grit SiC paper. Acrylic resin blocks were luted to the prepared dentine surfaces using HY Bond Temporary Cement Hard (HY), IP Temp Cement (IP), Fuji TEMP (FT) or Freegenol Temporary Cement (TC), and stored for 1 week. After removal of the temporary cements with an ultrasonic tip, the contact angle values of five specimens per test group were determined for the three test liquids, and the surface-energy parameters of the dentine surfaces were calculated. The dentine bond strengths of the self-adhesive cements were measured after removal of the temporary cements in a shear mode at a crosshead speed of 1.0mm/min. The data were subjected to one-way analysis of variance (ANOVA) followed by Tukey's HSD test. For all surfaces, the value of the estimated surface tension component γ(S)(d) (dispersion) was relatively constant at 41.7-43.3 mJm(-2). After removal of the temporary cements, the value of the γ(S)(h) (hydrogen-bonding) component decreased, particularly with FT and TC. The dentine bond strength of the self-adhesive cements was significantly higher for those without temporary cement contamination (8.2-10.6 MPa) than for those with temporary cement contamination (4.3-7.1 MPa). The γ(S) values decreased due to the decrease of γ(S)(h) values for the temporary cement-contaminated dentine. Contamination with temporary cements led to lower dentine bond strength. The presence of temporary cement interferes with the bonding performance of self-adhesive cements to dentine. Care should be taken in the methods of removal of temporary cement when using self-adhesive cements. Copyright © 2011 Elsevier Ltd. All rights reserved.

Nano-motion dynamics are determined by surface-tethered selectin mechanokinetics and bond formation.

Directory of Open Access Journals (Sweden)

Brian J Schmidt

2009-12-01

Full Text Available The interaction of proteins at cellular interfaces is critical for many biological processes, from intercellular signaling to cell adhesion. For example, the selectin family of adhesion receptors plays a critical role in trafficking during inflammation and immunosurveillance. Quantitative measurements of binding rates between surface-constrained proteins elicit insight into how molecular structural details and post-translational modifications contribute to function. However, nano-scale transport effects can obfuscate measurements in experimental assays. We constructed a biophysical simulation of the motion of a rigid microsphere coated with biomolecular adhesion receptors in shearing flow undergoing thermal motion. The simulation enabled in silico investigation of the effects of kinetic force dependence, molecular deformation, grouping adhesion receptors into clusters, surface-constrained bond formation, and nano-scale vertical transport on outputs that directly map to observable motions. Simulations recreated the jerky, discrete stop-and-go motions observed in P-selectin/PSGL-1 microbead assays with physiologic ligand densities. Motion statistics tied detailed simulated motion data to experimentally reported quantities. New deductions about biomolecular function for P-selectin/PSGL-1 interactions were made. Distributing adhesive forces among P-selectin/PSGL-1 molecules closely grouped in clusters was necessary to achieve bond lifetimes observed in microbead assays. Initial, capturing bond formation effectively occurred across the entire molecular contour length. However, subsequent rebinding events were enhanced by the reduced separation distance following the initial capture. The result demonstrates that vertical transport can contribute to an enhancement in the apparent bond formation rate. A detailed analysis of in silico motions prompted the proposition of wobble autocorrelation as an indicator of two-dimensional function. Insight into two

Influence of ultraviolet irradiation treatment on porcelain bond strength of titanium surfaces.

Science.gov (United States)

Kumasaka, Tomonari; Ohno, Akinori; Hori, Norio; Hoshi, Noriyuki; Maruo, Katsuichiro; Kuwabara, Atsushi; Seimiya, Kazuhide; Toyoda, Minoru; Kimoto, Katsuhiko

2018-01-26

To determine the effect of titanium (Ti) surface modification by ultraviolet irradiation (UVI) on the bond strength between Ti and porcelain. Grade 2 Ti plates were allotted to five groups: sandblasted (SA), 15 min UVI (UV), SA+5 min UVI (SA+UV5), SA+10 min UVI (SA+UV10), and SA+15 min UVI (SA+UV15). After surface treatment, porcelain was added. A precious metal (MC) was used for comparison with Ti. The effects of 24-h storage at room temperature versus thermal cycling only at 5 and 55°C in water were evaluated. Subsequently, the tensile strength of each sample was tested. Data were analyzed using one-way analysis of variance and the Tukey test. In both the room temperature and thermal cycling groups, the MC and SA+15 min UVI samples showed significantly greater bond strengths than the other samples (pbond strength between porcelain and the Ti surface.

The effect of dentine surface preparation and reduced application time of adhesive on bonding strength.

Science.gov (United States)

Saikaew, Pipop; Chowdhury, A F M Almas; Fukuyama, Mai; Kakuda, Shinichi; Carvalho, Ricardo M; Sano, Hidehiko

2016-04-01

This study evaluated the effects of surface preparation and the application time of adhesives on the resin-dentine bond strengths with universal adhesives. Sixty molars were cut to exposed mid-coronal dentine and divided into 12 groups (n=5) based on three factors; (1) adhesive: G-Premio Bond (GP, GC Corp., Tokyo, Japan), Clearfil Universal Bond (CU, Kuraray Noritake Dental Inc., Okayama, Japan) and Scotchbond Universal Adhesive (SB, 3M ESPE, St. Paul, MN, USA); (2) smear layer preparation: SiC paper ground dentine or bur-cut dentine; (3) application time: shortened time or as manufacturer's instruction. Fifteen resin-dentine sticks per group were processed for microtensile bond strength test (μTBS) according to non-trimming technique (1mm(2)) after storage in distilled water (37 °C) for 24h. Data were analyzed by three-way ANOVA and Dunnett T3 tests (α=0.05). Fractured surfaces were observed under scanning electron microscope (SEM). Another 12 teeth were prepared and cut into slices for SEM examination of bonded interfaces. μTBS were higher when bonded to SiC-ground dentine according to manufacturer's instruction. Bonding to bur-cut dentine resulted in significantly lower μTBS (padhesive resin interface. This was more pronounced when adhesives were bonded with a reduced application time and on bur cut dentine. The performance of universal adhesives can be compromised on bur cut dentine and when applied with a reduced application time. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effects of silane application on the shear bond strength of ceramic orthodontic brackets to enamel surface

Directory of Open Access Journals (Sweden)

Pinandi Sri Pudyani

2016-12-01

Full Text Available Background: Fixed orthodontic appliances with ceramic brackets are used frequently to fulfill the aesthetic demand of patient through orthodontic treatment. Ceramic brackets have some weaknesses such as bond strength and enamel surface damage. In high bond strength the risk of damage in enamel surfaces increases after debonding. Purpose: This study aimed to determine the effect of silane on base of bracket and adhesive to shear bond strength and enamel structure of ceramic bracket. Method: Sixteen extracted upper premolars were randomly divided into four groups based on silane or no silane on the bracket base and on the adhesive surface. Design of the base on ceramic bracket in this research was microcrystalline to manage the influence of mechanical interlocking. Samples were tested in shear mode on a universal testing machine after attachment. Following it, adhesive remnant index (ARI scores were used to assess bond failure site. Statistical analysis was performed using a two-way Anova and the Mann-Whitney test. A scanning electron microscope (SEM with a magnification of 2000x was used to observe enamel structure after debonding. Result: Shear bond strength was increased between group without silane and group with silane on the base of bracket (p<0,05. There was no significance different between group without silane and group with silane on adhesive (p<0,05. Conclusion: Application of silane on base of bracket increases shear bond strength, however, application of silane on adhesive site does not increase shear bond strength of ceramic bracket. Most bonding failure occurred at the enamel adhesive interface and damage occurred on enamel structure in group contains silane of ceramic bracket.

[Effects of surface treatment and adhesive application on shear bond strength between zirconia and enamel].

Science.gov (United States)

Li, Yinghui; Wu, Buling; Sun, Fengyang

2013-03-01

To evaluate the effects of sandblasting and different orthodontic adhesives on shear bond strength between zirconia and enamel. Zirconia ceramic samples were designed and manufactured for 40 extracted human maxillary first premolars with CAD/CAM system. The samples were randomized into 4 groups for surface treatment with sandblasting and non-treated with adhesives of 3M Transbond XT or Jingjin dental enamel bonding resin. After 24 h of bonded fixation, the shear bond strengths were measured by universal mechanical testing machine and analyzed with factorial variance analysis. The shear bond strength was significantly higher in sandblasting group than in untreated group (Padhesives of Transbond XT and dental enamel bonding resin (P>0.05). The shear bond strength between zirconia and enamel is sufficient after sandblasting regardless of the application of either adhesive.

Bond strength of resin-resin interfaces contaminated with saliva and submitted to different surface treatments

Directory of Open Access Journals (Sweden)

Adilson Yoshio Furuse

2007-12-01

Full Text Available The purpose of this study was to investigate the effect of different surface treatments on shear bond strength of saliva-contaminated resin-resin interfaces. Flat resin surfaces were fabricated. In the control group, no contamination or surface treatment was performed. The resin surfaces of the experimental groups were contaminated with saliva and air-dried, and then submitted to: (G1 rinsing with water and drying; (G2 application of an adhesive system; (G3 rinsing and drying, abrasion with finishing disks, etching and application of adhesive system; (G4 rinsing and drying, etching, application of silane and adhesive system. Resin cylinders were placed over the treated surfaces. The specimens were stored in water or ethanol. Shear bond strength tests were performed and the mode of failure was evaluated. Data were submitted to two-way ANOVA and Dunnett T3 test. Contamination of resin-resin interfaces with saliva significantly reduced shear strength, especially after prolonged storage (p<0.05. Similar values to the original bond strength were obtained after abrasion and application of adhesive (G3 or etching and application of silane and adhesive (G4. If contamination occurs, a surface treatment is required to guarantee an adequate interaction between the resin increments.

Effect of a New Surface Treatment Solution on the Bond Strength of Composite to Enamel

Science.gov (United States)

2016-06-01

Bond Strength of Composite to Enamel " is appropriately acknowledged and, beyond brief excerpts, is with the permission of the copyright owner...Solution on the Bond Strength of Composite to Enamel ABSTRACT Clean & Boost (Apex Dental Materials) is a novel surface treatment solution...designed to be used in place of phosphoric acid to increase the bond strength of self-etch adhesives to enamel and more effectively remove contaminants

Enhancing structural integrity of adhesive bonds through pulsed laser surface micro-machining

KAUST Repository

Diaz, Edwin Hernandez

2015-06-01

Enhancing the effective peel resistance of plastically deforming adhesive joints through laser-based surface micro-machining Edwin Hernandez Diaz Inspired by adhesion examples commonly found in nature, we reached out to examine the effect of different kinds of heterogeneous surface properties that may replicate this behavior and the mechanisms at work. In order to do this, we used pulsed laser ablation on copper substrates (CuZn40) aiming to increase adhesion for bonding. A Yb-fiber laser was used for surface preparation of the substrates, which were probed with a Scanning Electron Microscope (SEM) and X-ray Photoelectron Spectroscopy (XPS). Heterogeneous surface properties were devised through the use of simplified laser micromachined patterns which may induce sequential events of crack arrest propagation, thereby having a leveraging effect on dissipation. The me- chanical performance of copper/epoxy joints with homogeneous and heterogeneous laser micromachined interfaces was then analyzed using the T-peel test. Fractured surfaces were analyzed using SEM to resolve the mechanism of failure and adhesive penetration within induced surface asperities from the treatment. Results confirm positive modifications of the surface morphology and chemistry from laser ablation that enable mechanical interlocking and cohesive failure within the adhesive layer. Remarkable improvements of apparent peel energy, bond toughness, and effective peel force were appreciated with respect to sanded substrates as control samples.

Influence of different surface treatments on push‑out bond strengths ...

African Journals Online (AJOL)

2015-06-26

Jun 26, 2015 ... perpendicularly along the long axis of the post using a saw. Two disks ... Arslan, et al.: Effect of laser on bond ... Untreated fiber posts have a comparatively smooth surface area that .... Soares CJ, Valdivia AD, da Silva GR, Santana FR, Menezes Mde S. Longitudinal ... Dent Mater 2006;22:752‑8. 7. Ferrari M ...

Influencing the bonding and assembly of a multiterminal molecule on a metal surface

Energy Technology Data Exchange (ETDEWEB)

Lukas, Maya; Doessel, Kerrin; Fink, Karin; Fuhr, Olaf [Karlsruhe Institute of Technology (KIT), Institute of Nanotechnology, D-76021 Karlsruhe (Germany); DFG Center of Functional Nanostructures (CFN), D-76049 Karlsruhe (Germany); Schramm, Alexandrina; Stroh, Christophe [Karlsruhe Institute of Technology (KIT), Institute of Nanotechnology, D-76021 Karlsruhe (Germany); Mayor, Marcel [Karlsruhe Institute of Technology (KIT), Institute of Nanotechnology, D-76021 Karlsruhe (Germany); DFG Center of Functional Nanostructures (CFN), D-76049 Karlsruhe (Germany); University of Basel, Department of Chemistry, CH-4056 Basel (Switzerland); Loehneysen, Hilbert von [Karlsruhe Institute of Technology (KIT), Institute of Nanotechnology, D-76021 Karlsruhe (Germany); DFG Center of Functional Nanostructures (CFN), D-76049 Karlsruhe (Germany); Karlsruhe Institute of Technology (KIT), Physics Institute and Institute for Solid State Physics, D-76049 Karlsruhe (Germany)

2011-07-01

The bond of a molecule to a metallic electrode is known to have a crucial influence on the molecular conductance. As electronic functionalities are integrated into molecules or several subunits are connected to a three-dimensional multiterminal molecule, it is not obvious that a ''well-known'' chemical linker group will lead to the bonding configuration known from simpler molecules. We investigated a series of tripodal molecules on metal surfaces by STM. The chemical linker groups and the complex connecting the three wire-units are varied. We find that the position of molecules on the surface is governed by a subtle balance of intermolecular and molecule-surface interactions, partly in strong contrast to expectations. This emphasizes the need to characterize the nature of molecule-electrode contacts along with the investigation of the electronic conductance.

Atom-specific look at the surface chemical bond using x-ray emission spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Nilsson, A.; Wassdahl, N.; Weinelt, M. [Uppsala Univ. (Sweden)] [and others

1997-04-01

CO and N{sub 2} adsorbed on the late transition metals have become prototype systems regarding the general understanding of molecular adsorption. It is in general assumed that the bonding of molecules to transition metals can be explained in terms of the interaction of the frontier HOMO and LUMO molecular orbitals with the d-orbitals. In such a picture the other molecular orbitals should remain essentially the same as in the free molecule. For the adsorption of the isoelectronic molecules CO and N{sub 2} this has led to the so called Blyholder model i.e., a synergetic {sigma} (HOMO) donor and {pi} (LUMO) backdonation bond. The authors results at the ALS show that such a picture is oversimplified. The direct observation and identification of the states related to the surface chemical bond is an experimental challenge. For noble and transition metal surfaces, the adsorption induced states overlap with the metal d valence band. Their signature is therefore often obscured by bulk substrate states. This complication has made it difficult for techniques such as photoemission and inverse photoemission to provide reliable information on the energy of chemisorption induced states and has left questions unanswered regarding the validity of the frontier orbitals concept. Here the authors show how x-ray emission spectroscopy (XES), in spite of its inherent bulk sensitivity, can be used to investigate adsorbed molecules. Due to the localization of the core-excited intermediate state, XE spectroscopy allows an atomic specific separation of the valence electronic states. Thus the molecular contributions to the surface measurements make it possible to determine the symmetry of the molecular states, i.e., the separation of {pi} and {sigma} type states. In all the authors can obtain an atomic view of the electronic states involved in the formation of the chemical bond to the surface.

A parametric study of surface roughness and bonding mechanisms of aluminum alloys with epoxies: a molecular dynamics simulation

Science.gov (United States)

Timilsina, Rajendra; Termaath, Stephanie

The marine environment is highly aggressive towards most materials. However, aluminium-magnesium alloys (Al-Mg, specifically, 5xxx series) have exceptionally long service life in such aggressive marine environments. For instance, an Al-Mg alloy, AA5083, is extensively used in naval structures because of its good mechanical strength, formability, seawater corrosion resistance and weldability. However, bonding mechanisms of these alloys with epoxies in a rough surface environment are not fully understood yet. It requires a rigorous investigation at molecular or atomic levels. We performed a molecular dynamics simulation to study an adherend surface preparation and surface bonding mechanisms of Al-Mg alloy (AA5083) with different epoxies by developing several computer models. Various distributions of surface roughness are introduced in the models and performed molecular dynamics simulations. Formation of a beta phase (Al3Mg2) , microstructures, bonding energies at the interface, bonding strengths and durability are investigated. Office of Naval Research.

Effects of hardness of abrasive grains on surface roughness of work piece in PVA bonded grinding wheel

International Nuclear Information System (INIS)

Nitta, S.; Takata, A.; Ishizaki, K.

2000-01-01

The purpose of this study is to clarify relation between hardness of abrasive grains and surface roughness of work piece in the case of PVA (Polyvinyl alcohol) bonded grinding wheels. Two PVA bonded grinding wheels; with diamond or silicon carbide as abrasive grains and grinding of glass and aluminum alloy was performed. The PVA bonded grinding wheels The PVA bonded grinding wheel with silicon carbide could not grind the glass. Because insufficiency in hardness, the PVA bonded grinding wheel with the diamond abrasive grains caused deep scratch on the aluminum alloy. It was found that the final surface roughness of the work piece was not proportional to the hardness of abrasive grains. The suitable hardness of abrasive grains will be obtained by the hardness of work piece. Copyright (2000) AD-TECH - International Foundation for the Advancement of Technology Ltd

Surface bond contraction and its effect on the nanometric sized lead zirconate titanate

International Nuclear Information System (INIS)

Haitao Huang; Sun, Chang Q.; Hing, Peter

2000-01-01

The grain size effect of lead zirconate titanate PbZr 1-x Ti x O 3 (PZT, x≥0.6) caused by surface bond contraction has been investigated by using the Landau-Ginsburg-Devonshire (LGD) phenomenological theory. It has been shown that, due to the surface bond contraction, both the Curie temperature and the spontaneous polarization of tetragonal PZT decrease with decreasing grain size. These effects become more significant when the grain size is in the nanometre range. A dielectric anomaly appears with decreasing grain size, which corresponds to a size dependent phase transformation. The ferroelectric critical size below which a loss of ferroelectricity will happen is estimated from the results obtained. (author). Letter-to-the-editor

In Vitro Evaluation of Various Surface Treatments of Fiber Posts on the Bond Strength to Composite Core

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Sareh Nadalizadeh

Full Text Available Introduction: The reliable bond at the root-post-core interface is critical for the clinical success of post-retained restorations. To decrease the risk of fracture, it is important to optimize the adhesion. Therefore, various post surface treatments have been proposed. The purpose of this study was to investigate the influence of various surface treatments of fiber posts on the bond strength to composite core. Materials & Methods: In this study, 40 fiber reinforced posts were used. After preparing and sectioning them, resulting specimens were divided into four groups (N=28. The posts received different surface treatments such as no surface treatment (control group, preparing with hydrogen peroxide 10%, preparing with silane, preparing with HF and silane. Then, posts were tested in micro tensile testing machine. The results were analyzed by One-Way ANOVA and Dunnett T3 test. Results: The greatest bond strength observed was in treatment with hydrogen peroxide 10% (19.84±8.95 MPa, and the lowest strength was related to the control group (12.44±3.40 MPa. The comparison of the groups with Dunnett T3 test showed that the differences between the groups was statistically significant (α=0.05.Conclusion: Based on the results of this study, preparing with H2O2 -10 % and silane increases the bond strength of FRC posts to the composite core more than the other methods. Generally, the bond strength of posts to the composite core increases by surface treatment.

A comparative effect of various surface chemical treatments on the resin composite-composite repair bond strength

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Shaloo Gupta

2015-01-01

Full Text Available Aim: The aim of this in vitro study was an attempt to investigate the effect of different surface treatments on the bond strength between pre-existing composite and repair composite resin. Materials and Methods: Forty acrylic blocks were prepared in a cuboidal mould. In each block, a well of 5 mm diameter and 5 mm depth was prepared to retain the composite resin (Filtek™ Z350, 3M/ESPE. Aging of the composite discs was achieved by storing them in water at 37°C for 1 week, and after that were divided into 5 groups (n = 8 according to surface treatment: Group I- 37% phosphoric acid, Group II-10% hydrofluoric acid, Group III-30% citric acid, Group IV-7% maleic acid and Group V- Adhesive (no etchant. The etched surfaces were rinsed and dried followed by application of bonding agent (Adper™ Single Bond 2. 3M/ESPE. The repair composite was placed on aged composite, light-cured for 40 seconds and stored in water at 37°C for 1 week. Shear bond strength between the aged and the new composite resin was determined with a universal testing machine (crosshead speed of 0.5 mm/min. Statistical Analysis: The compressive shear strengths were compared for differences using ANOVA test followed by Tamhane′s T2 post hoc analysis. Results: The surface treatment with 10% hydrofluoric acid showed the maximum bond strength followed by 30% citric acid, 7% maleic acid and 37% phosphoric acid in decreasing order. Conclusion: The use of 10% hydrofluoric acid can be a good alternative for surface treatment in repair of composite resin restoration as compared to commonly used 37% orthophosphoric acid.

Study of the adsorption, electronic structure and bonding of C2H4 on the FeNi(1 1 1) surface

International Nuclear Information System (INIS)

Simonetti, S.; Brizuela, G.; Juan, A.

2010-01-01

The adsorption of C 2 H 4 on the FeNi(1 1 1) alloy surface has been studied by ASED-MO tight binding calculations. The C 2 H 4 molecule presents its most stable geometry with the C=C bond axis parallel to the surface along the [1, -1, 0] direction, bonded on top Fe atom and bonded along a Fe-Fe bridge site. As a consequence, the strength of the local Fe-Fe bond decreases between 37 and 62% of its original bulk value. This bond weakening is mainly due to the new C-Fe interactions however no Fe 3 C carbide formation is evidenced on surface. The Fe-Ni and Ni-Ni superficial bonds are only slightly modified.

Effect of artificial aging and surface treatment on bond strengths to dental zirconia.

Science.gov (United States)

Perdigão, J; Fernandes, S D; Pinto, A M; Oliveira, F A

2013-01-01

The objective of this project was to study the influence of artificial aging and surface treatment on the microtensile bond strengths (μTBS) between zirconia and a phosphate monomer-based self-adhesive cement. Thirty zirconia disks (IPS e.max ZirCAD, Ivoclar Vivadent) were randomly assigned to two aging regimens: AR, used as received, which served as a control, and AG, artificial aging to simulate low-temperature degradation. Subsequently, the disks of each aging regimen were assigned to three surface treatments: NT, no surface treatment; CO, surface silicatization with CoJet sand (3M ESPE); and ZP, zirconia surface treated with Z-Prime Plus (Bisco Inc). Thirty discs were made of Filtek Z250 (3M ESPE) composite resin and luted to the zirconia discs using RelyX Unicem (3M ESPE). The specimens were sectioned with a diamond blade in X and Y directions to obtain bonded beams with a cross-section of 1.0 ± 0.2 mm. The beams were tested in tensile mode in a universal testing machine at a speed of 0.5 mm/min to measure μTBS. Selected beams were selected for fractographic analysis under the SEM. Statistical analysis was carried out with two-way analysis of variance and Dunnett T3 post hoc test at a significance level of 95%. The mean μTBS for the three AR subgroups (AR-NT, AR-CO, and AR-ZP) were significantly higher than those of the corresponding AG groups (p<0.0001). Both AR-CO and AR-ZP resulted in statistically significant higher mean bond strengths than the group AR-NT (p<0.006 and p<0.0001, respectively). Both AG-CO and AG-ZP resulted in statistically significant higher mean bond strengths than the group AG-NT (both at p<0.0001). Overall, AG decreased mean μTBS. Under the SEM, mixed failures showed residual cement attached to the zirconia side of the beams. CO resulted in a characteristic roughness of the zirconia surface. AR-ZP was the only group for which the amount of residual cement occupied at least 50% of the interface in mixed failures.

Effects of surface treatments on bond strength of dental Ti-20Cr and Ti-10Zr alloys to porcelain

International Nuclear Information System (INIS)

Lin, Hsi-Chen; Wu, Shih-Ching; Ho, Wen-Fu; Huang, Ling-Hsiu; Hsu, Hsueh-Chuan

2010-01-01

The purpose of this study was to investigate the effect of surface treatments, including sandblasting and grinding, on the bond strength between a low-fusing porcelain and c.p. Ti, Ti-20Cr and Ti-10Zr alloys. The surface treatments were divided into 2 groups. Grinding surface treatment was applied to the first group, which served as the control, and sandblasting was applied to the second group. After treatment, low-fusing porcelain (Titankeramik) was fired onto the surface of the specimens. A universal testing machine was used to perform a 3-point bending test. The metal-ceramic interfaces were subjected to scanning electron microscopic analysis. Of the sandblasted samples, the debonding test showed that Ti-20Cr alloy had the strongest (31.50 MPa) titanium-ceramic bond (p < 005), followed by c.p. Ti (29.4 MPa) and Ti-10Zr (24.3 MPa). Of the grinded samples, Ti-20Cr alloy showed 27.3 MPa titanium-ceramic bond (p < 005), followed by c.p. Ti (14.3 MPa) and Ti-10Zr (failure). The SEM micrographs of the metal surface after debonding showed residual porcelain retained on all samples. On the whole, sandblasting surface treatment appears to have had a more beneficial effect on the Ti-ceramic bond strength than grinding surface treatment. Furthermore, surface treatment of Ti-20Cr with either grinding or sandblasting resulted in adequate bond strength, which exceeded the lower limit value in the ISO 9693 standard (25 MPa).

Determination of the bonding of alkyl monolayers to the Si(111) surface using chemical-shift, scanned-energy photoelectron diffraction

Energy Technology Data Exchange (ETDEWEB)

Terry, J.; Linford, M.R.; Wigren, C.; Cao, R.; Pianetta, P.; Chidsey, C.E. [Stanford University, Stanford, California 94309 (United States)

1997-08-01

The bonding of alkyl monolayers to Si(111) surfaces has been studied by conventional x-ray photoelectron spectroscopy (XPS) and chemical-shift, scanned-energy photoelectron diffraction (PED) using synchrotron radiation. Two very different wet-chemical methods have been used to prepare the alkyl monolayers: (i) olefin insertion into the H{endash}Si bond on the H{endash}Si(111) surface, and (ii) replacement of Cl on the Cl{endash}Si(111) surface by an alkyl group from an alkyllithium reagent. In both cases, XPS has revealed a C 1s signal chemically shifted to lower binding energy, which we have assigned to carbon bonded to silicon. PED has shown that both preparative methods result in carbon bonded in an atop site with the expected C{endash}Si bond length of 1.85{plus_minus}0.05{Angstrom}. Chemical-shift, scanned-energy photoelectron diffraction is a particularly valuable probe of local structure at surfaces that contain the same element in multiple, chemically distinct environments. {copyright} {ital 1997 American Institute of Physics.}

Determination of the bonding of alkyl monolayers to the Si(111) surface using chemical-shift, scanned-energy photoelectron diffraction

International Nuclear Information System (INIS)

Terry, J.; Linford, M.R.; Wigren, C.; Cao, R.; Pianetta, P.; Chidsey, C.E.

1997-01-01

The bonding of alkyl monolayers to Si(111) surfaces has been studied by conventional x-ray photoelectron spectroscopy (XPS) and chemical-shift, scanned-energy photoelectron diffraction (PED) using synchrotron radiation. Two very different wet-chemical methods have been used to prepare the alkyl monolayers: (i) olefin insertion into the H endash Si bond on the H endash Si(111) surface, and (ii) replacement of Cl on the Cl endash Si(111) surface by an alkyl group from an alkyllithium reagent. In both cases, XPS has revealed a C 1s signal chemically shifted to lower binding energy, which we have assigned to carbon bonded to silicon. PED has shown that both preparative methods result in carbon bonded in an atop site with the expected C endash Si bond length of 1.85±0.05 Angstrom. Chemical-shift, scanned-energy photoelectron diffraction is a particularly valuable probe of local structure at surfaces that contain the same element in multiple, chemically distinct environments. copyright 1997 American Institute of Physics

Strength and failure analysis of composite-to-composite adhesive bonds with different surface treatments

Science.gov (United States)

Paranjpe, Nikhil; Alamir, Mohammed; Alonayni, Abdullah; Asmatulu, Eylem; Rahman, Muhammad M.; Asmatulu, Ramazan

2018-03-01

Adhesives are widely utilized materials in aviation, automotive, energy, defense, and marine industries. Adhesive joints are gradually supplanting mechanical fasteners because they are lightweight structures, thus making the assembly lighter and easier. They also act as a sealant to prevent a structural joint from galvanic corrosion and leakages. Adhesive bonds provide high joint strength because of the fact that the load is distributed uniformly on the joint surface, while in mechanical joints, the load is concentrated at one point, thus leading to stress at that point and in turn causing joint failures. This research concentrated on the analysis of bond strength and failure loads in adhesive joint of composite-to-composite surfaces. Different durations of plasma along with the detergent cleaning were conducted on the composite surfaces prior to the adhesive applications and curing processes. The joint strength of the composites increased about 34% when the surface was plasma treated for 12 minutes. It is concluded that the combination of different surface preparations, rather than only one type of surface treatment, provides an ideal joint quality for the composites.

Determination of wafer bonding mechanisms for plasma activated SiN films with x-ray reflectivity

Energy Technology Data Exchange (ETDEWEB)

Hayashi, S [Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095 (United States); Sandhu, R [Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095 (United States); Wojtowicz, M [Northrop Grumman Space Technology, Redondo Beach, CA 90278 (United States); Sun, Y [Department of Chemical Engineering, University of California, Los Angeles, CA 90095 (United States); Hicks, R [Department of Chemical Engineering, University of California, Los Angeles, CA 90095 (United States); Goorsky, M S [Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095 (United States)

2005-05-21

Specular and diffuse x-ray reflectivity measurements were employed for wafer bonding studies of surface and interfacial reactions in {approx}800 A thick SiN films deposited on III-V substrates. CuK{sub {alpha}}{sub 1} radiation was employed for these measurements. The as-deposited films show very low surface roughness and uniform, high density SiN. Reflectivity measurements show that an oxygen plasma treatment converts the nitride surface to a somewhat porous SiO{sub x} layer (67 A thick, at 80% of SiO{sub 2} density), with confirmation of the oxide formation from x-ray photoelectron spectroscopy. Reactions at the bonded interface of two oxygen plasma treated SiN layers were examined using a bonded structure from which one of the III-V wafers is removed. Reflectivity measurements of bonded structures annealed at 150 deg. C and 300 deg. C show an increase in the SiO{sub x} layer density and thickness and even a density gradient across this interface. The increase in density is correlated with an increase in bond strength, where after the 300 deg. C anneal, a high interfacial bond strength, exceeding the bulk strength, was achieved.

Effect of surface treatments on the bond strength of soft denture lining materials to an acrylic resin denture base.

Science.gov (United States)

Gundogdu, Mustafa; Yesil Duymus, Zeynep; Alkurt, Murat

2014-10-01

Adhesive failure between acrylic resin and resilient liner material is commonly encountered in clinical practice. The purpose of this study was to evaluate the effect of different surface treatments on the bond strength of 2 different resilient lining materials to an acrylic resin denture base. Ninety-six dumbbell-shaped specimens were fabricated from heat-polymerized acrylic resin, and 3 mm of the material was cut from the thin midsection. The specimens were divided into 6 groups according to their surface treatments: no surface treatment (control group), 36% phosphoric acid etching (acid group), erbium:yttrium-aluminum-garnet (Er:YAG) laser (laser group), airborne-particle abrasion with 50-μm Al2O3 particles (abrasion group), an acid+laser group, and an abrasion+laser group. The specimens in each group were divided into 2 subgroups according to the resilient lining material used: heat-polymerized silicone based resilient liner (Molloplast B) and autopolymerized silicone-based resilient liner (Ufi Gel P). After all of the specimens had been polymerized, they were stored in distilled water at 37°C for 1 week. A tensile bond strength test was then performed. Data were analyzed with a 2-way ANOVA, and the Sidak multiple comparison test was used to identify significant differences (α=.05). The effects of the surface treatments and resilient lining materials on the surface of the denture base resin were examined with scanning electron microscopy. The tensile bond strength was significantly different between Molloplast B and Ufi Gel P (P<.001). The specimens of the acid group had the highest tensile bond strength, whereas those of the abrasion group had the lowest tensile bond strength. The scanning electron microscopy observations showed that the application of surface treatments modified the surface of the denture base resin. Molloplast B exhibited significantly higher bond strength than Ufi Gel P. Altering the surface of the acrylic resin denture base with 36

Effect of Four Methods of Surface Treatment on Shear Bond Strength of Orthodontic Brackets to Zirconium

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Soghra Yassaei

2015-10-01

Full Text Available Objectives: Providing reliable attachment between bracket base and zirconia surface is a prerequisite for exertion of orthodontic force. The purpose of the present study was to eval- uate the effect of four zirconium surface treatment methods on shear bond strength (SBS of orthodontic brackets.Materials and Methods: One block of zirconium was trimmed into four zirconium sur- faces, which served as our four study groups and each had 18 metal brackets bonded to them. Once the glazed layer was removed, the first group was etched with 9.6% hydrofluoric acid (HF, and the other three groups were prepared by means of sandblasting and 1 W, and 2 W Er: YAG laser, respectively. After application of silane, central incisor brackets were bonded to the zirconium surfaces. The SBS values were measured by a Dartec testing ma- chine with a crosshead speed of 1 mm/min.Results: The highest SBS was achieved in the sandblasted group (7.81±1.02 MPa followed in a descending order by 2 W laser group (6.95±0.87 MPa, 1 W laser group (6.87±0.92MPa and HF acid etched group (5.84±0.78 MPa. The differences between the study groups, were statistically significant except between the laser groups (P < 0.05. Conclusion: In terms of higher bond strength and safety, sandblasting and Er: YAG laser irradiation with power output of 1 W and 2 W can be considered more appropriate alterna- tives to HF acid etching for zirconium surface treatment prior to bracket bonding.

Effect of Different Surface Treatments on Repair Micro-shear Bond Strength of Silica- and Zirconia-filled Composite Resins

Directory of Open Access Journals (Sweden)

Mohammad Joulaei

2012-11-01

Full Text Available Background and aims. Effect of surface treatments on repair bond strength of aged composite resins might be different due to their dissimilar fillers. The aim was to evaluate the effect of different surface treatments on repair micro-shear bond strength (µSBS of silica- (Spectrum TPH and zirconia-filled (Filtek Z250 composite resins. Materials and methods. Twenty-seven composite resin blocks were made from each type of composite resin: Z250 and Spectrum TPH. After aging, blocks of each type were randomly divided into three groups according to surface treatments: alloy primer, silane, and only surface roughening. Subsequently, each group was further subdivided into 3 subgroups based on the adhesive system used: Single Bond, Clearfil SE Bond, and Margin Bond. Four composite resin columns were added on each block. After thermocycling, µSBStest were done at cross head speed of 0.5 mm/min. Data was analysed using multifactor ANOVA, one-way ANOVA and a post-hoc Bonferroni tests (α = 0.05. Results. Analysis of data showed that the effect of composite resin type was not significant (p > 0.05, but the effects of the type of surface treatment (p = 0.01 and the type of adhesive system (p = 0.01 were significant on repair µSBS. In addition, the cumulative effect of the composite type-surface treatment and the composite type with the type of adhesive system were not statistically significant (p > 0.05. However, the cumulative effects of the adhesive system-surface treatment (p = 0.03 and the composite type-the adhesive system-surface treatments (p = 0.002 were significant. Conclusion. Although repair µSBS values of both silica- and zirconia-filled composite resins were similar, use of different combinations of surface treatments and adhesive systems affected their repair µSBS differently.

Effect of Different Surface Treatments on Repair Micro-shear Bond Strength of Silica- and Zirconia-filled Composite Resins

Science.gov (United States)

Joulaei, Mohammad; Bahari, Mahmoud; Ahmadi, Anahid; Savadi Oskoee, Siavash

2012-01-01

Background and aims Effect of surface treatments on repair bond strength of aged composite resins might be different due to their dissimilar fillers. The aim was to evaluate the effect of different surface treatments on repair micro-shear bond strength (µSBS) of silica- (Spectrum TPH) and zirconia-filled (Filtek Z250) composite resins. Materials and methods Twenty-seven composite resin blocks were made from each type of composite resin: Z250 and Spectrum TPH. After aging, blocks of each type were randomly divided into three groups according to surface treatments: alloy primer, silane, and only surface roughening. Subsequently, each group was further subdivided into 3 subgroups based on the adhesive system used: Single Bond, Clearfil SE Bond, and Margin Bond. Four composite resin columns were added on each block. After thermocycling, µSBStest were done at cross head speed of 0.5 mm/min. Data was analysed using multifactor ANOVA, one-way ANOVA and a post-hoc Bonferroni tests (α = 0.05). Results Analysis of data showed that the effect of composite resin type was not significant (p > 0.05), but the effects of the type of surface treatment (p = 0.01) and the type of adhesive system (p = 0.01) were significant on repair µSBS. In addition, the cumulative effect of the composite type-surface treatment and the composite type with the type of adhesive system were not statistically significant (p > 0.05). However, the cumulative effects of the adhesive system-surface treatment (p = 0.03) and the composite type-the adhesive system-surface treatments (p = 0.002) were significant. Conclusion Although repair µSBS values of both silica- and zirconia-filled composite resins were similar, use of different combinations of surface treatments and adhesive systems affected their repair µSBS differently. PMID:23277859

Incorporation of TiO2 nanotubes in a polycrystalline zirconia: Synthesis of nanotubes, surface characterization, and bond strength.

Science.gov (United States)

Dos Santos, Angélica Feltrin; Sandes de Lucena, Fernanda; Sanches Borges, Ana Flávia; Lisboa-Filho, Paulo Noronha; Furuse, Adilson Yoshio

2018-04-05

Despite numerous advantages such as high strength, the bond of yttria-stabilized zirconia polycrystal (Y-TZP) to tooth structure requires improvement. The purpose of this in vitro study was to evaluate the incorporation of TiO 2 nanotubes into zirconia surfaces and the bond strength of resin cement to the modified ceramic. TiO 2 nanotubes were produced by alkaline synthesis, mixed with isopropyl alcohol (50 wt%) and applied on presintered zirconia disks. The ceramics were sintered, and the surfaces were characterized by confocal laser microscopy, scanning electron microscopy (SEM), and energy-dispersive x-ray spectroscopy (EDS) analysis. For bond strength, the following 6 groups (n=16) were evaluated: without TiO 2 and Single Bond Universal; with TiO 2 nanotubes and Single Bond Universal; without TiO 2 nanotubes and Z-prime; with TiO 2 nanotubes and Z-prime; without TiO 2 and Signum Zirconia Bond; with TiO 2 and Signum Zirconia Bond. After sintering, resin cement cylinders, diameter of 1.40 mm and 1 mm in height, were prepared and polymerized for 20 seconds. Specimens were stored in water at 37°C for 30 days and submitted to a shear test. Data were analyzed by 2-way ANOVA and Tukey honest significant difference (α=.05) tests. EDS analysis confirmed that nanoagglomerates were composed of TiO 2 . The shear bond strength showed statistically significant differences among bonding agents (P<.001). No significant differences were found with the application of nanotubes, regardless of the group analyzed (P=.682). The interaction among the bonding agent factors and addition of nanotubes was significant (P=.025). Nanotubes can be incorporated into zirconia surfaces. However, this incorporation did not improve bond strength. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

75 FR 50772 - Agency Information Collection Activities: Importation Bond Structure

Science.gov (United States)

2010-08-17

... DEPARTMENT OF HOMELAND SECURITY U.S. Customs and Border Protection Agency Information Collection Activities: Importation Bond Structure AGENCY: U.S. Customs and Border Protection, Department of Homeland... information collection requirement concerning the: Importation Bond Structure. This request for comment is...

Effect of Ti:sapphire laser on shear bond strength of orthodontic brackets to ceramic surfaces.

Science.gov (United States)

Erdur, Emire Aybuke; Basciftci, Faruk Ayhan

2015-08-01

With increasing demand for orthodontic treatments in adults, orthodontists continue to debate the optimal way to prepare ceramic surfaces for bonding. This study evaluated the effects of a Ti:sapphire laser on the shear bond strength (SBS) of orthodontic brackets bonded to two ceramic surfaces (feldspathic and IPS Empress e-Max) and the results were compared with those using two other lasers (Er:YAG and Nd:YAG) and 'conventional' techniques, i.e., sandblasting (50 µm) and hydrofluoric (HF) acid. In total, 150 ceramic discs were prepared and divided into two groups. In each group, the following five subgroups were prepared: Ti:sapphire laser, Nd:YAG laser, Er:YAG laser, sandblasting, and HF acid. Mandibular incisor brackets were bonded using a light-cured adhesive. The samples were stored in distilled water for 24 hours at 37°C and then thermocycled. Extra samples were prepared and examined using scanning electron microscopy (SEM). SBS testing was performed and failure modes were classified. ANOVA and Tukey's HSD tests were used to compare SBS among the five subgroups (P < 0.05). Feldspathic and IPS Empress e-Max ceramics had similar SBS values. The Ti:sapphire femtosecond laser (16.76 ± 1.37 MPa) produced the highest mean bond strength, followed by sandblasting (12.79 ± 1.42 MPa) and HF acid (11.28 ± 1.26 MPa). The Er:YAG (5.43 ± 1.21 MPa) and Nd:YAG laser (5.36 ± 1.04 MPa) groups were similar and had the lowest SBS values. More homogeneous and regular surfaces were observed in the ablation pattern with the Ti:sapphire laser than with the other treatments by SEM analysis. Within the limitations of this in vitro study, Ti:sapphire laser- treated surfaces had the highest SBS values. Therefore, this technique may be useful for the pretreatment of ceramic surfaces as an alternative to 'conventional' techniques. © 2015 Wiley Periodicals, Inc.

Theoretical aspects of methyl acetate and methanol activation on MgO(100) and (501) catalyst surfaces with application in FAME production

Energy Technology Data Exchange (ETDEWEB)

Man, Isabela-Costinela, E-mail: isabela.man@g.unibuc.ro [University of Bucharest, Faculty of Chemistry, Department of Organic Chemistry, Biochemistry and Catalysis, 4-12 Regina Elisabeta Av., S3, 030018 Bucharest (Romania); Romanian Academy, ‘C.D. Nenitzescu’ Center of Organic Chemistry, 202B Spl. Independentei, 060023 Bucharest (Romania); Soriga, Stefan Gabriel [University Politehnica of Bucharest, Centre for Technology Transfer in the Process Industries, 1, Gh. Polizu Street, Building A, Room A056, RO-011061 Bucharest (Romania); Parvulescu, Vasile [University of Bucharest, Faculty of Chemistry, Department of Organic Chemistry, Biochemistry and Catalysis, 4-12 Regina Elisabeta Av., S3, 030018 Bucharest (Romania)

2017-01-15

Highlights: • Energetics of C−O and C−H bond dissociation and formation of MeOAc on MgO(100) indicate that the bond formations are favorable. • Energetics of C−O and C−H bond dissociation and formation of MeOAc on MgO(501) indicate that the C−O bond dissociation and C−H bond formations are favorable. • The coadsorbed MeOH facilitate O−H bond dissociation of MeOH compared to isolated molecule. • Provide further understanding of reactivity of MgO surfaces with application in transesterification and interesterification reactions. - Abstract: Density functional theory (DFT) calculations were carried out to study the activation of methyl acetate and methanol on MgO(100) and MgO(501) surfaces and integrated in the context of transesterification, interesterification and glycerolysis reactions used in biodiesel industry. First results indicate the importance of including of dispersion forces in the calculations. On MgO(100) the reverse reactions steps of C−O and C−H dissociations and on MgO(501) the same reverse reaction step of C−H dissociations of methyl acetate are energetically favorable, while the dissociation of C−O bond into methoxide and acetate fragments on the edge of MgO(501) was found to be exothermic with a low activation energy. For methanol, the dissociation of O−H bond on MgO(100) surface in the presence of the second coadsorbed methanol molecule becomes more energetically favoured compared to the isolated molecule, due to the fact that the methoxide fragment is stabilized by intermolecular hydrogen bonding. This is reflected by the decrease of the activation energy of the forward reaction step and the increase of the activation energy of the backward reaction step, increasing the probability to have dissociated molecules among the undissociated ones. These results represent a step forward for better understanding from atomistic point of view the paths of these reactions on these surfaces for the corresponding catalytic

Surface analysis applied to metal-ceramic and bioceramic interfacial bonding

International Nuclear Information System (INIS)

Smart, R.St.C.; Arora, P.S.; Steveson, M.; Kawashima, N.; Cavallaro, G.P.; Ming, H.; Skinner, W.M.

1999-01-01

Full text: Low temperature plasma reactions, combined with sol-gel coatings, have been used to produce a variety of ceramic surface layers on metal substrates and interfacial layers between metals and oxides or other ceramics. These layers can be designed to be compositionally and functionally graded from the metal to bulk ceramic material, eg. silica, alumina, hydroxyapatite. The graded layers are generally <50nm thick, continuous, fully bonded to the substrate and deformable without disbonding. The objectives in design of these layers have been to produce: metal surfaces protected from oxidation, corrosion and acid attack; improved metal-ceramic bonding; and bioceramic titanium-based interfaces to bioactive hydroxyapatite for improved dental and medical implants. Modified Auger parameter studies for Si in XPS spectra show that the structure on the metal surfaces grades from amorphous, dehydroxylated silica on the outer surface through layer silicates, chain silicates, pyrosilicates to orthosilicates close to the metal interface. At the metal interface, detached grains of the metal are imaged with interpenetration of the oxide and silicate species linking the layer to the oxidised metal surface. The ∼30nm layer has a substantially increased frictional load compared with the untreated oxidised metal, i.e. behaviour consistent with either stronger adhesion of the coating to the substrate or a harder surface. The composition, structure and thickness of these layers can be controlled by the duration of each plasma reaction and the choice of the final reagent. The mechanisms of reaction in each process step have been elucidated with a combination of XPS, TOF-SIMS, TEM, SEM and FTIR. Similar, graded titanium/oxide/silicate/silica ceramic surface layers have been shown to form using the low temperature plasma reactions on titanium alloys used in medical and dental implants. Thicker (i.e. μm) overlayers of ceramic materials can be added to the graded surface layers

Controlling hydrogenation activity and selectivity of bimetallic surfaces and catalysts

Science.gov (United States)

Murillo, Luis E.

Studies of bimetallic systems are of great interest in catalysis due to the novel properties that they often show in comparison with the parent metals. The goals of this dissertation are: (1) to expand the studies of self-hydrogenation and hydrogenation reactions on bimetallic surfaces under ultra high vacuum conditions (UHV) using different hydrocarbon as probe molecules; (2) to attempt to correlate the surface science findings with supported catalyst studies under more realistic conditions; and (3) to investigate the competitive hydrogenation of C=C versus C=O bonds on Pt(111) modified by different 3d transition metals. Hydrogenation studies using temperature programmed desorption (TPD) on Ni/Pt(111) bimetallic surfaces have demonstrated an enhancement in the low temperature hydrogenation activity relative to that of clean Pt(111). This novel hydrogenation pathway can be achieved under UHV conditions by controlling the structures of the bimetallic surfaces. A low temperature hydrogenation activity of 1-hexene and 1-butene has been observed on a Pt-Ni-Pt(111) subsurface structure, where Ni atoms are mainly present on the second layer of the Pt(111) single crystal. These results are in agreement with previous studies of self-hydrogenation and hydrogenation of cyclohexene. However, a much higher dehydrogenation activity is observed in the reaction of cyclohexene to produce benzene, demonstrating that the hydrocarbon structure has an effect on the reaction pathways. On the other hand, self-hydrogenation of 1-butene is not observed on the Pt-Ni-Pt(111) surface, indicating that the chain length (or molecular weight) has a significant effect on the selfhydrogenation activity. The gas phase reaction of cyclohexene on Ni/Pt supported on alumina catalysts has also shown a higher self-hydrogenation activity in comparison with the same reaction performed on supported monometallic catalysts. The effects of metal loading and impregnation sequence of the metal precursors are

Enhancing structural integrity of adhesive bonds through pulsed laser surface micro-machining

KAUST Repository

Diaz, Edwin Hernandez

2015-01-01

of different kinds of heterogeneous surface properties that may replicate this behavior and the mechanisms at work. In order to do this, we used pulsed laser ablation on copper substrates (CuZn40) aiming to increase adhesion for bonding. A Yb-fiber laser

Ab initio characterization of coupling strength for all types of dangling-bond pairs on the hydrogen-terminated Si(100)-2 × 1 surface

Science.gov (United States)

Shaterzadeh-Yazdi, Zahra; Sanders, Barry C.; DiLabio, Gino A.

2018-04-01

Recent work has suggested that coupled silicon dangling bonds sharing an excess electron may serve as building blocks for quantum-cellular-automata cells and quantum computing schemes when constructed on hydrogen-terminated silicon surfaces. In this work, we employ ab initio density-functional theory to examine the details associated with the coupling between two dangling bonds sharing one excess electron and arranged in various configurations on models of phosphorous-doped hydrogen-terminated silicon (100) surfaces. Our results show that the coupling strength depends strongly on the relative orientation of the dangling bonds on the surface and on the separation between them. The orientation of dangling bonds is determined by the anisotropy of the silicon (100) surface, so this feature of the surface is a significant contributing factor to variations in the strength of coupling between dangling bonds. The results demonstrate that simple models for approximating tunneling, such as the Wentzel-Kramer-Brillouin method, which do not incorporate the details of surface structure, are incapable of providing reasonable estimates of tunneling rates between dangling bonds. The results provide guidance to efforts related to the development of dangling-bond based computing elements.

Effect of surface treatment of prefabricated posts on bonding of resin cement

DEFF Research Database (Denmark)

Sahafi, Alireza; Peutzfeld, Anne; Asmussen, Erik

2004-01-01

This in vitro study evaluated the effect of various surface treatments of prefabricated posts of titanium alloy (ParaPost XH), glass fiber (ParaPost Fiber White) and zirconia (Cerapost) on the bonding of two resin cements: ParaPost Cement and Panavia F by a diametral tensile strength (DTS) test...... the start of mixing the resin cement, the specimen was freed from the mold and stored in water at 37 degrees C for seven days. Following water storage, the specimen was wet-ground to a final length of approximately 3 mm. The DTS of specimens was determined in a Universal Testing Machine. The bonding...

Effect of different surface treatments on the shear bond strength of nanofilled composite repairs

Directory of Open Access Journals (Sweden)

Ghazaleh Ahmadizenouz

2016-03-01

Full Text Available Background. Repairing aged composite resin is a challenging process. Many surface treatment options have been proposed to this end. This study evaluated the effect of different surface treatments on the shear bond strength (SBS of nano-filled composite resin repairs. Methods. Seventy-five cylindrical specimens of a Filtek Z350XT composite resin were fabricated and stored in 37°C distilled water for 24 hours. After thermocycling, the specimens were divided into 5 groups according to the following surface treatments: no treatment (group 1; air abrasion with 50-μm aluminum oxide particles (group 2; irradiation with Er:YAG laser beams (group 3; roughening with coarse-grit diamond bur + 35% phosphoric acid (group 4; and etching with 9% hydrofluoric acid for 120 s (group 5. Another group of Filtek Z350XT composite resin samples (4×6 mm was fabricated for the measurement of cohesive strength (group 6. A silane coupling agent and an adhesive system were applied after each surface treatment. The specimens were restored with the same composite resin and thermocycled again. A shearing force was applied to the interface in a universal testing machine. Data were analyzed using one-way ANOVA and post hoc Tukey tests (P < 0.05. Results. One-way ANOVA indicated significant differences between the groups (P < 0.05. SBS of controls was significantly lower than the other groups; differences between groups 2, 3, 4, 5 and 6 were not significant. Surface treatment with diamond bur + 35% phosphoric acid resulted in the highest bond strength. Conclusion. All the surface treatments used in this study improved the shear bond strength of nanofilled composite resin used.

Bonding polycarbonate brackets to ceramic: : Effects of substrate treatment on bond strength

NARCIS (Netherlands)

Özcan, Mutlu; Vallittu, Pekka K.; Peltomäki, Timo; Huysmans, Marie-Charlotte; Kalk, Warner

2004-01-01

This study evaluated the effects of 5 different surface conditioning methods on the bond strength of polycarbonate brackets bonded to ceramic surfaces with resin based cement. Six disc-shaped ceramic specimens (feldspathic porcelain) with glazed surfaces were used for each group. The specimens were

Dentine bond strength and antimicrobial activity evaluation of adhesive systems.

Science.gov (United States)

André, Carolina Bosso; Gomes, Brenda Paula Figueiredo Almeida; Duque, Thais Mageste; Stipp, Rafael Nobrega; Chan, Daniel Chi Ngai; Ambrosano, Glaucia Maria Bovi; Giannini, Marcelo

2015-04-01

This study evaluated the dentine bond strength (BS) and the antibacterial activity (AA) of six adhesives against strict anaerobic and facultative bacteria. Three adhesives containing antibacterial components (Gluma 2Bond (glutaraldehyde)/G2B, Clearfil SE Protect (MDPB)/CSP and Peak Universal Bond (PUB)/chlorhexidine) and the same adhesive versions without antibacterial agents (Gluma Comfort Bond/GCB, Clearfil SE Bond/CSB and Peak LC Bond/PLB) were tested. The AA of adhesives and control groups was evaluated by direct contact method against four strict anaerobic and four facultative bacteria. After incubation, according to the appropriate periods of time for each microorganism, the time to kill microorganisms was measured. For BS, the adhesives were applied according to manufacturers' recommendations and teeth restored with composite. Teeth (n=10) were sectioned to obtain bonded beams specimens, which were tested after artificial saliva storage for one week and one year. BS data were analyzed using two-way ANOVA and Tukey test. Saliva storage for one year reduces the BS only for GCB. In general G2B and GCB required at least 24h for killing microorganisms. PUB and PLB killed only strict anaerobic microorganisms after 24h. For CSP the average time to eliminate the Streptococcus mutans and strict anaerobic oral pathogens was 30 min. CSB showed no AA against facultative bacteria, but had AA against some strict anaerobic microorganisms. Storage time had no effect on the BS for most of the adhesives. The time required to kill bacteria depended on the type of adhesive and never was less than 10 min. Most of the adhesives showed stable bond strength after one year and the Clearfil SE Protect may be a good alternative in restorative procedures performed on dentine, considering its adequate bond strength and better antibacterial activity. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effect of Bonding Pressure and Bonding Time on the Tensile Properties of Cu-Foam / Cu-Plate Diffusion Bonded Joint

International Nuclear Information System (INIS)

Kim, Sang-Ho; Heo, Hoe-Jun; Kang, Chung-Yun; Yoon, Tae-Jin

2016-01-01

Open cell Cu foam, which has been widely utilized in various industries because of its high thermal conductivity, lightweight and large surface area, was successfully joined with Cu plate by diffusion bonding. To prevent excessive deformation of the Cu foam during bonding process, the bonding pressure should be lower than 500 kPa at 800 ℃ for 60 min and bonding pressure should be lowered with increasing holding time. The bonding strength was evaluated by tensile tests. The tensile load of joints increased with the bonding pressure and holding time. In the case of higher bonding pressure or time, the bonded length at the interface was usually longer than the cross-sectional length of the foam, so fracture occurred at the foam. For the same reason, base metal (foam) fracture mainly occurred at the node-plate junction rather than in the strut-plate junction because the bonded surface area of the node was relatively larger than that of the strut.

Antibacterial Activity of Commercial Dentine Bonding Systems against E. faecalis–Flow Cytometry Study

Directory of Open Access Journals (Sweden)

Monika Lukomska-Szymanska

2017-04-01

Full Text Available Literature presents inconsistent results on the antibacterial activity of dentine bonding systems (DBS. Antibacterial activity of adhesive systems depends on several factors, including composition and acidity. Flow cytometry is a novel detection method to measure multiple characteristics of a single cell: total cell number, structural (size, shape, and functional parameters (viability, cell cycle. The LIVE/DEAD® BacLightTM bacterial viability assay was used to evaluate an antibacterial activity of DBS by assessing physical membrane disruption of bacteria mediated by DBS. Ten commercial DBSs: four total-etching (TE, four self-etching (SE and two selective enamel etching (SEE were tested. Both total-etching DBS ExciTE F and OptiBond Solo Plus showed comparatively low antibacterial activity against E. faecalis. The lowest activity of all tested TE systems showed Te-Econom Bond. Among SE DBS, G-ænial Bond (92.24% dead cells followed by Clearfil S3 Bond Plus (88.02% and Panavia F 2.0 ED Primer II (86.67% showed the highest antibacterial activity against E. faecalis, which was comparable to isopropranol (positive control. In the present study, self-etching DBS exhibited higher antimicrobial activity than tested total-etching adhesives against E. faecalis.

Comparison of Degrees of Potential-Energy-Surface Anharmonicity for Complexes and Clusters with Hydrogen Bonds

Science.gov (United States)

Kozlovskaya, E. N.; Doroshenko, I. Yu.; Pogorelov, V. E.; Vaskivskyi, Ye. V.; Pitsevich, G. A.

2018-01-01

Previously calculated multidimensional potential-energy surfaces of the MeOH monomer and dimer, water dimer, malonaldehyde, formic acid dimer, free pyridine-N-oxide/trichloroacetic acid complex, and protonated water dimer were analyzed. The corresponding harmonic potential-energy surfaces near the global minima were constructed for series of clusters and complexes with hydrogen bonds of different strengths based on the behavior of the calculated multidimensional potential-energy surfaces. This enabled the introduction of an obvious anharmonicity parameter for the calculated potential-energy surfaces. The anharmonicity parameter was analyzed as functions of the size of the analyzed area near the energy minimum, the number of points over which energies were compared, and the dimensionality of the solved vibrational problem. Anharmonicity parameters for potential-energy surfaces in complexes with strong, medium, and weak H-bonds were calculated under identical conditions. The obtained anharmonicity parameters were compared with the corresponding diagonal anharmonicity constants for stretching vibrations of the bridging protons and the lengths of the hydrogen bridges.

Metal-free oxidative olefination of primary amines with benzylic C-H bonds through direct deamination and C-H bond activation.

Science.gov (United States)

Gong, Liang; Xing, Li-Juan; Xu, Tong; Zhu, Xue-Ping; Zhou, Wen; Kang, Ning; Wang, Bin

2014-09-14

An oxidative olefination reaction between aliphatic primary amines and benzylic sp(3) C-H bonds has been achieved using N-bromosuccinimide as catalyst and tert-butyl hydroperoxide as oxidant. The olefination proceeds under mild metal-free conditions through direct deamination and benzylic C-H bond activation, and provides easy access to biologically active 2-styrylquinolines with (E)-configuration.

Effect of surface treatment of titanium posts on the tensile bond strength

NARCIS (Netherlands)

Schmage, P; Sohn, J; Ozcan, M; Nergiz, [No Value

Objectives. Retention of composite resins to metal can be improved when metal surfaces are conditioned. The purpose of this investigation was to investigate the effect of two conditioning treatments on the tensile bond strength of four resin-based luting cements and zinc phosphate cement to titanium

Chemical activation of molecules by metals: Experimental studies of electron distributions and bonding

International Nuclear Information System (INIS)

Lichtenberger, D.L.

1991-10-01

The formal relationship between measured molecular ionization energies and thermodynamic bond dissociation energies has been developed into a single equation which unifies the treatment of covalent bonds, ionic bonds, and partially ionic bonds. This relationship has been used to clarify the fundamental thermodynamic information relating to metal-hydrogen, metal-alkyl, and metal-metal bond energies. We have been able to obtain a direct observation and measurement of the stabilization energy provided by the agostic interaction of the C-H bond with the metal. The ionization energies have also been used to correlate the rates of carbonyl substitution reactions of (η 5 -C 5 H 4 X)Rh(CO) 2 complexes, and to reveal the electronic factors that control the stability of the transition state. The extent that the electronic features of these bonding interactions transfer to other chemical systems is being investigated in terms of the principle of additivity of ligand electronic effects. Specific examples under study include metal- phosphines, metal-halides, and metallocenes. Especially interesting has been the recent application of these techniques to the characterization of the soccer-ball shaped C 60 molecule, buckminsterfullerene, and its interaction with a metal surface. The high-resolution valence ionizations in the gas phase reveal the high symmetry of the molecule, and studies of thin films of C 60 reveal weak intermolecular interactions. Scanning tunneling and atomic force microscopy reveal the arrangement of spherical molecules on gold substrates, with significant delocalization of charge from the metal surface. 21 refs

Reactive Landing of Gramicidin S and Ubiquitin Ions onto Activated Self-Assembled Monolayer Surfaces

Energy Technology Data Exchange (ETDEWEB)

Laskin, Julia; Hu, Qichi

2017-03-13

Using mass-selected ion deposition combined with in situ infrared reflection absorption spectroscopy (IRRAS), we examined the reactive landing of gramicidin S and ubiquitin ions onto activated self-assembled monolayer (SAM) surfaces terminated with N-hydroxysuccinimidyl ester (NHS-SAM) and acyl fluoride (COF-SAM) groups. Doubly protonated gramicidin S, [GS+2H]2+, and two charge states of ubiquitin, [U+5H]5+ and [U+13H]13+, were used as model systems, allowing us to explore the effect of the number of free amino groups and the secondary structure on the efficiency of covalent bond formation between the projectile ion and the surface. For all projectile ions, ion deposition resulted in the depletion of IRRAS bands corresponding to the terminal groups on the SAM and the appearance of several new bands not associated with the deposited species. These new bands were assigned to the C=O stretching vibrations of COOH and COO- groups formed on the surface as a result of ion deposition. The presence of these bands was attributed to an alternative reactive landing pathway that competes with covalent bond formation. This pathway with similar yields for both gramicidin S and ubiquitin ions is analogous to the hydrolysis of the NHS ester bond in solution. The covalent bond formation efficiency increased linearly with the number of free amino groups and was found to be lower for the more compact conformation of ubiquitin compared with the fully unfolded conformation. This observation was attributed to the limited availability of amino groups on the surface of the folded conformation. Our results have provided new insights on the efficiency and mechanism of reactive landing of peptides and proteins onto activated SAMs

c-C5H5 on a Ni(1 1 1) surface: Theoretical study of the adsorption, electronic structure and bonding

International Nuclear Information System (INIS)

German, E.; Simonetti, S.; Pronsato, E.; Juan, A.; Brizuela, G.

2008-01-01

In the present work the ASED-MO method is applied to study the adsorption of cyclopentadienyl anion on a Ni(1 1 1) surface. The adsorption with the centre of the aromatic ring placed above the hollow position has been identified to be energetically the most favourable. The aromatic ring remains almost flat, the H atoms are tilted 17 deg. away from the metal surface. We modelled the metal surface by a two-dimensional slab of finite thickness, with an overlayer of c-C 5 H 5 - , one c-C 5 H 5 - per nine surface Ni atoms. The c-C 5 H 5 - molecule is attached to the surface with its five C atoms bonding mainly with three Ni atoms. The Ni-Ni bond in the underlying surface and the C-C bonds of c-C 5 H 5 - are weakened upon adsorption. We found that the band of Ni 5d z 2 orbitals plays an important role in the bonding between c-C 5 H 5 - and the surface, as do the Ni 6s and 6p z bands

Pre-treatments applied to oxidized aluminum surfaces to modify the interfacial bonding with bis-1,2-(triethoxysilyl)ethane (BTSE)

Energy Technology Data Exchange (ETDEWEB)

Teo, M. [Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T 1Z1 (Canada); Kim, J. [Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T 1Z1 (Canada); Wong, P.C. [Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T 1Z1 (Canada); Wong, K.C. [Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T 1Z1 (Canada); Mitchell, K.A.R. [Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T 1Z1 (Canada)]. E-mail: karm@chem.ubc.ca

2005-12-15

A remote microwave-generated H{sub 2} plasma and heating to 250 deg. C were separately used to modify high-purity oxidized aluminum surfaces and to assess whether these treatments can help enhance adhesion with bis-1,2-(triethoxysilyl)ethane (BTSE) coatings. Different initial oxide surfaces were considered, corresponding to the native oxide and to surfaces formed by the Forest Products Laboratory (FPL) treatment applied for either 15 or 60 min. BTSE is applied from solution at pH 4, and competing processes of etching, protonation (to form OH groups) and coupling (to form Al-O-Si interfacial bonds) occur at the solid-liquid interface. Scanning electron microscopy (SEM) was used to determine how the topographies of the modified Al surfaces changed with the different pre-treatments and with exposure to a buffer solution of pH 4. Secondary-ion mass spectrometry (SIMS) was used to determine the direct amount of Al-O-Si interfacial bonds by measuring the ratio of peak intensities 71-70 amu, while X-ray photoelectron spectroscopy (XPS) was used to determine the overall strength of the silane coating adhesion by measuring the Si 2p signals before and after application of an ultrasonic rinse to the coated sample. Measured Al 2p and O 1s spectra helped assess how the different pre-treatments modified the various Al oxidized surfaces prior to BTSE coating. Pre-treated samples that showed increased Al-O-Si bonding after BTSE coating corresponded to surfaces, which did not show evidence of significant etching after exposure to a pH 4 environment. This suggests that such surfaces are more receptive to the coupling reaction during exposure to the BTSE coating solution. These surfaces include all H{sub 2} plasma-treated samples, the heated native oxide and the sample that only received the 15 min FPL treatment. In contrast, other surfaces that show evidence of etching in pH 4 environments are samples that received lower amounts of Al-O-Si interfacial bonding. Overall, heating

Porous surface modified bioactive bone cement for enhanced bone bonding.

Directory of Open Access Journals (Sweden)

Qiang He

Full Text Available Polymethylmethacrylate bone cement cannot provide an adhesive chemical bonding to form a stable cement-bone interface. Bioactive bone cements show bone bonding ability, but their clinical application is limited because bone resorption is observed after implantation. Porous polymethylmethacrylate can be achieved with the addition of carboxymethylcellulose, alginate and gelatin microparticles to promote bone ingrowth, but the mechanical properties are too low to be used in orthopedic applications. Bone ingrowth into cement could decrease the possibility of bone resorption and promote the formation of a stable interface. However, scarce literature is reported on bioactive bone cements that allow bone ingrowth. In this paper, we reported a porous surface modified bioactive bone cement with desired mechanical properties, which could allow for bone ingrowth.The porous surface modified bioactive bone cement was evaluated to determine its handling characteristics, mechanical properties and behavior in a simulated body fluid. The in vitro cellular responses of the samples were also investigated in terms of cell attachment, proliferation, and osteoblastic differentiation. Furthermore, bone ingrowth was examined in a rabbit femoral condyle defect model by using micro-CT imaging and histological analysis. The strength of the implant-bone interface was also investigated by push-out tests.The modified bone cement with a low content of bioactive fillers resulted in proper handling characteristics and adequate mechanical properties, but slightly affected its bioactivity. Moreover, the degree of attachment, proliferation and osteogenic differentiation of preosteoblast cells was also increased. The results of the push-out test revealed that higher interfacial bonding strength was achieved with the modified bone cement because of the formation of the apatite layer and the osseointegration after implantation in the bony defect.Our findings suggested a new bioactive

Effects of femtosecond laser and other surface treatments on the bond strength of metallic and ceramic orthodontic brackets to zirconia.

Science.gov (United States)

García-Sanz, Verónica; Paredes-Gallardo, Vanessa; Bellot-Arcís, Carlos; Mendoza-Yero, Omel; Doñate-Buendía, Carlos; Montero, Javier; Albaladejo, Alberto

2017-01-01

Femtosecond laser has been proposed as a method for conditioning zirconia surfaces to boost bond strength. However, metallic or ceramic bracket bonding to femtosecond laser-treated zirconia surfaces has not been tested. This study compared the effects of four conditioning techniques, including femtosecond laser irradiation, on shear bond strength (SBS) of metallic and ceramic brackets to zirconia.Three hundred zirconia plates were divided into five groups: 1) control (C); 2) sandblasting (APA); 3) silica coating and silane (SC); 4) femtosecond laser (FS); 5) sandblasting followed by femtosecond laser (APA+SC). A thermal imaging camera measured temperature changes in the zirconia during irradiation. Each group was divided into 2 subgroups (metallic vs ceramic brackets). SBS was evaluated using a universal testing machine. The adhesive remnant index (ARI) was registered and surfaces were observed under SEM. Surface treatment and bracket type significantly affected the bracket-zirconia bond strength. SBS was significantly higher (pbrackets in all groups (APA+FS > APA > FS > SC > control) than metallic brackets (APA+FS > FS > SC > APA > control). For metallic brackets, groups SC (5.99 ± 1.86 MPa), FS (6.72 ± 2.30 MPa) and APA+FS (7.22 ± 2.73 MPa) reported significantly higher bond strengths than other groups (p brackets, the highest bond strength values were obtained in groups APA (25.01 ± 4.45 MPa), FS (23.18 ± 6.51 MPa) and APA+FS (29.22 ± 8.20 MPa).Femtosecond laser enhances bond strength of ceramic and metallic brackets to zirconia. Ceramic brackets provide significantly stronger adhesion than metallic brackets regardless of the surface treatment method.

Effect of surface treatment of prefabricated teeth on shear bond strength of orthodontic brackets.

Science.gov (United States)

Cumerlato, Marina; Lima, Eduardo Martinelli de; Osorio, Leandro Berni; Mota, Eduardo Gonçalves; Menezes, Luciane Macedo de; Rizzatto, Susana Maria Deon

2017-01-01

The aim of this in vitro study was to evaluate and compare the effects of grinding, drilling, sandblasting, and ageing prefabricated teeth (PfT) on the shear bond strength (SBS) of orthodontic brackets, as well as the effects of surface treatments on the adhesive remnant index (ARI). One-hundred-ninety-two PfT were divided into four groups (n = 48): Group 1, no surface treatment was done; Group 2, grinding was performed with a cylindrical diamond bur; Group 3, two drillings were done with a spherical diamond bur; Group 4, sandblasting was performed with 50-µm aluminum oxide. Before the experiment, half of the samples stayed immersed in distilled water at 37oC for 90 days. Brackets were bonded with Transbond XT and shear strength tests were carried out using a universal testing machine. SBS were compared by surface treatment and by ageing with two-way ANOVA, followed by Tukey's test. ARI scores were compared between surface treatments with Kruskal-Wallis test followed by Dunn's test. Surface treatments on PfT enhanced SBS of brackets (pgrinding) (pgrinding. There was a positive correlation between SBS and ARI.

Shear Bond Strength of Three Orthodontic Bonding Systems on Enamel and Restorative Materials.

Science.gov (United States)

Hellak, Andreas; Ebeling, Jennifer; Schauseil, Michael; Stein, Steffen; Roggendorf, Matthias; Korbmacher-Steiner, Heike

2016-01-01

Objective. The aim of this in vitro study was to determine the shear bond strength (SBS) and adhesive remnant index (ARI) score of two self-etching no-mix adhesives (iBond ™ and Scotchbond ™ ) on different prosthetic surfaces and enamel, in comparison with the commonly used total etch system Transbond XT ™ . Materials and Methods . A total of 270 surfaces (1 enamel and 8 restorative surfaces, n = 30) were randomly divided into three adhesive groups. In group 1 (control) brackets were bonded with Transbond XT primer. In the experimental groups iBond adhesive (group 2) and Scotchbond Universal adhesive (group 3) were used. The SBS was measured using a Zwicki 1120 ™ testing machine. The ARI and SBS were compared statistically using the Kruskal-Wallis test ( P ≤ 0.05). Results . Significant differences in SBS and ARI were found between the control group and experimental groups. Conclusions . Transbond XT showed the highest SBS on human enamel. Scotchbond Universal on average provides the best bonding on all other types of surface (metal, composite, and porcelain), with no need for additional primers. It might therefore be helpful for simplifying bonding in orthodontic procedures on restorative materials in patients. If metal brackets have to be bonded to a metal surface, the use of a dual-curing resin is recommended.

Comparative evaluation of tensile bond strength of silicone-based denture liners after thermocycling and surface treatment.

Science.gov (United States)

Kaur, Harsimran; Datta, Kusum

2015-01-01

To examine, evaluate, and compare the tensile bond strength of two silicone-based liners; one autopolymerizing and one heat cured, when treated with different chemical etchants to improve their adhesion with denture base resin. Hundred and sixty test specimens of heat-cured polymethyl methacrylate (PMMA) were fabricated; out of which 80 specimens were tested for tensile bond strength after bonding it to autopolymerizing resilient liner (Ufigel P) and rest 80 to heat-cured resilient liner (Molloplast B). Each main group was further divided into four subgroups of 20 specimens each, one to act as a control and three were subjected to surface treatment with different chemical etchants namely dichloromethane, MMA monomer, and chloroform. The two silicone-based denture liners were processed between 2 PMMA specimens (10 mm × 10 mm × 40 mm) in the space provided by a spacer of 3 mm, thermocycled (5-55°C) for 500 cycles, and then their tensile strength measurements were done in the universal testing machine. One-way ANOVA technique showed a highly significant difference in the mean tensile bond strength values for all the groups. The Student's t-test computed values of statistics for the compared groups were greater than the critical values both at 5% and at 1% levels. Surface treatment of denture base resin with chemical etchants prior to the application of silicone-based liner (Ufigel P and Molloplast-B) increased the tensile bond strength. The increase was the highest with specimens subjected to 180 s of MMA surface treatment and the lowest with control group specimens.

The Effect of Phosphoric Acid Pre-etching Times on Bonding Performance and Surface Free Energy with Single-step Self-etch Adhesives.

Science.gov (United States)

Tsujimoto, A; Barkmeier, W W; Takamizawa, T; Latta, M A; Miyazaki, M

2016-01-01

The purpose of this study was to evaluate the effect of phosphoric acid pre-etching times on shear bond strength (SBS) and surface free energy (SFE) with single-step self-etch adhesives. The three single-step self-etch adhesives used were: 1) Scotchbond Universal Adhesive (3M ESPE), 2) Clearfil tri-S Bond (Kuraray Noritake Dental), and 3) G-Bond Plus (GC). Two no pre-etching groups, 1) untreated enamel and 2) enamel surfaces after ultrasonic cleaning with distilled water for 30 seconds to remove the smear layer, were prepared. There were four pre-etching groups: 1) enamel surfaces were pre-etched with phosphoric acid (Etchant, 3M ESPE) for 3 seconds, 2) enamel surfaces were pre-etched for 5 seconds, 3) enamel surfaces were pre-etched for 10 seconds, and 4) enamel surfaces were pre-etched for 15 seconds. Resin composite was bonded to the treated enamel surface to determine SBS. The SFEs of treated enamel surfaces were determined by measuring the contact angles of three test liquids. Scanning electron microscopy was used to examine the enamel surfaces and enamel-adhesive interface. The specimens with phosphoric acid pre-etching showed significantly higher SBS and SFEs than the specimens without phosphoric acid pre-etching regardless of the adhesive system used. SBS and SFEs did not increase for phosphoric acid pre-etching times over 3 seconds. There were no significant differences in SBS and SFEs between the specimens with and without a smear layer. The data suggest that phosphoric acid pre-etching of ground enamel improves the bonding performance of single-step self-etch adhesives, but these bonding properties do not increase for phosphoric acid pre-etching times over 3 seconds.

30 CFR 942.800 - Bond and insurance requirements for surface coal mining and reclamation operations.

Science.gov (United States)

2010-07-01

... required for postmining water treatment must remain bonded. However, the trust fund or annuity may serve as... coal mining and reclamation operations. 942.800 Section 942.800 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR PROGRAMS FOR THE CONDUCT OF SURFACE MINING...

Spectroscopic characterization of a single dangling bond on a bare Si(100)- c ( 4 × 2 ) surface for n - and p -type doping

KAUST Repository

Mantega, M.

2012-07-19

We investigate the charging state of an isolated single dangling bond formed on an unpassivated Si(100) surface with c(4×2) reconstruction, by comparing scanning tunneling microscopy and spectroscopy analysis with density functional theory calculations. The dangling bond is created by placing a single hydrogen atom on the bare surface with the tip of a scanning tunneling microscope. The H atom passivates one of the dimer dangling bonds responsible for the surface one-dimensional electronic structure. This leaves a second dangling at the reacted surface dimer which breaks the surface periodicity. We consider two possible H adsorption configurations for both the neutral and the doped situation (n- and p-type). In the case of n-doping we find that the single dangling bond state is doubly occupied and the most stable configuration is that with H bonded to the bottom Si atom of the surface dimer. In the case of p-doping the dangling bond is instead empty and the configuration with the H attached to the top atom of the dimer is the most stable. Importantly the two configurations have different scattering properties and phase shift fingerprints. This might open up interesting perspectives for fabricating a switching device by tuning the doping level or by locally charging the single dangling bond state. © 2012 American Physical Society.

Spectroscopic characterization of a single dangling bond on a bare Si(100)- c ( 4 × 2 ) surface for n - and p -type doping

KAUST Repository

Mantega, M.; Rungger, I.; Naydenov, B.; Boland, J. J.; Sanvito, S.

2012-01-01

We investigate the charging state of an isolated single dangling bond formed on an unpassivated Si(100) surface with c(4×2) reconstruction, by comparing scanning tunneling microscopy and spectroscopy analysis with density functional theory calculations. The dangling bond is created by placing a single hydrogen atom on the bare surface with the tip of a scanning tunneling microscope. The H atom passivates one of the dimer dangling bonds responsible for the surface one-dimensional electronic structure. This leaves a second dangling at the reacted surface dimer which breaks the surface periodicity. We consider two possible H adsorption configurations for both the neutral and the doped situation (n- and p-type). In the case of n-doping we find that the single dangling bond state is doubly occupied and the most stable configuration is that with H bonded to the bottom Si atom of the surface dimer. In the case of p-doping the dangling bond is instead empty and the configuration with the H attached to the top atom of the dimer is the most stable. Importantly the two configurations have different scattering properties and phase shift fingerprints. This might open up interesting perspectives for fabricating a switching device by tuning the doping level or by locally charging the single dangling bond state. © 2012 American Physical Society.

Microfluidic DNA microarrays in PMMA chips: streamlined fabrication via simultaneous DNA immobilization and bonding activation by brief UV exposure

DEFF Research Database (Denmark)

Sabourin, David; Petersen, J; Snakenborg, Detlef

2010-01-01

This report presents and describes a simple and scalable method for producing functional DNA microarrays within enclosed polymeric, PMMA, microfluidic devices. Brief (30 s) exposure to UV simultaneously immobilized poly(T)poly(C)-tagged DNA probes to the surface of unmodified PMMA and activated...... the surface for bonding below the glass transition temperature of the bulk PMMA. Functionality and validation of the enclosed PMMA microarrays was demonstrated as 18 patients were correctly genotyped for all eight mutation sites in the HBB gene interrogated. The fabrication process therefore produced probes...... with desired hybridization properties and sufficient bonding between PMMA layers to allow construction of microfluidic devices. The streamlined fabrication method is suited to the production of low-cost microfluidic microarray-based diagnostic devices and, as such, is equally applicable to the development...

DNA base dimers are stabilized by hydrogen-bonding interactions including non-Watson-Crick pairing near graphite surfaces.

Science.gov (United States)

Shankar, Akshaya; Jagota, Anand; Mittal, Jeetain

2012-10-11

Single- and double-stranded DNA are increasingly being paired with surfaces and nanoparticles for numerous applications, such as sensing, imaging, and drug delivery. Unlike the majority of DNA structures in bulk that are stabilized by canonical Watson-Crick pairing between Ade-Thy and Gua-Cyt, those adsorbed on surfaces are often stabilized by noncanonical base pairing, quartet formation, and base-surface stacking. Not much is known about these kinds of interactions. To build an understanding of the role of non-Watson-Crick pairing on DNA behavior near surfaces, one requires basic information on DNA base pair stacking and hydrogen-bonding interactions. All-atom molecular simulations of DNA bases in two cases--in bulk water and strongly adsorbed on a graphite surface--are conducted to study the relative strengths of stacking and hydrogen bond interactions for each of the 10 possible combinations of base pairs. The key information obtained from these simulations is the free energy as a function of distance between two bases in a pair. We find that stacking interactions exert the dominant influence on the stability of DNA base pairs in bulk water as expected. The strength of stability for these stacking interactions is found to decrease in the order Gua-Gua > Ade-Gua > Ade-Ade > Gua-Thy > Gua-Cyt > Ade-Thy > Ade-Cyt > Thy-Thy > Cyt-Thy > Cyt-Cyt. On the other hand, mutual interactions of surface-adsorbed base pairs are stabilized mostly by hydrogen-bonding interactions in the order Gua-Cyt > Ade-Gua > Ade-Thy > Ade-Ade > Cyt-Thy > Gua-Gua > Cyt-Cyt > Ade-Cyt > Thy-Thy > Gua-Thy. Interestingly, several non-Watson-Crick base pairings, which are commonly ignored, have similar stabilization free energies due to interbase hydrogen bonding as Watson-Crick pairs. This clearly highlights the importance of non-Watson-Crick base pairing in the development of secondary structures of oligonucleotides near surfaces.

Further Investigation Into the Use of Laser Surface Preparation of Ti-6Al-4V Alloy for Adhesive Bonding

Science.gov (United States)

Palmieri, Frank L.; Crow, Allison; Zetterberg, Anna; Hopkins, John; Wohl, Christopher J.; Connell, John W.; Belcher, Tony; Blohowiak, Kay Y.

2014-01-01

Adhesive bonding offers many advantages over mechanical fastening, but requires robust materials and processing methodologies before it can be incorporated in primary structures for aerospace applications. Surface preparation is widely recognized as one of the key steps to producing robust and predictable bonds. This report documents an ongoing investigation of a surface preparation technique based on Nd:YAG laser ablation as a replacement for the chemical etch and/or abrasive processes currently applied to Ti-6Al-4V alloys. Laser ablation imparts both topographical and chemical changes to a surface that can lead to increased bond durability. A laser based process provides an alternative to chemical-immersion, manual abrasion, and grit blast process steps which are expensive, hazardous, environmentally unfriendly, and less precise. In addition, laser ablation is amenable to process automation, which can improve reproducibility to meet quality standards for surface preparation. An update on work involving adhesive property testing, surface characterization, surface stability, and the effect of laser surface treatment on fatigue behavior is presented. Based on the tests conducted, laser surface treatment is a viable replacement for the immersion chemical surface treatment processes. Testing also showed that the fatigue behavior of the Ti-6Al-4V alloy is comparable for surfaces treated with either laser ablation or chemical surface treatment.

Examining the free radical bonding mechanism of benzoquinone– and hydroquinone–methanol passivation of silicon surfaces

International Nuclear Information System (INIS)

Kotulak, Nicole A.; Chen, Meixi; Schreiber, Nikolas; Jones, Kevin; Opila, Robert L.

2015-01-01

Highlights: • Photons are required for high levels of c-Si passivation by both BQ/ME and HQ/ME solutions. • Protons are required for high levels of c-Si passivation by both BQ/ME and HQ/ME solutions. • The free radical QH· is the likely passivating species for c-Si surfaces from BQ/ME and HQ/ME solutions. - Abstract: The surface passivation of p-benzoquinone (BQ) and hydroquinone (HQ) when dissolved in methanol (ME) has been examined through effective lifetime testing of crystalline silicon (c-Si) wafers treated with the aforementioned solutions. Changes in the availability of both photons and protons in the solutions were demonstrated to affect the level of passivation achieved. The requirement of both excess protons and ambient light exposure to maintain high effective lifetimes supports the presence of a free radical species that drives the surface passivation. Surface analysis suggests a 1:1 ratio of HQ-like bonds to methoxy bonds on the c-Si surface after treatment with a BQ/ME solution.

Surface Characterization of Some Novel Bonded Phase Packing Materials for HPLC Columns Using MAS-NMR Spectroscopy

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Jude Abia

2015-03-01

Full Text Available Information on the surface properties of three novel chemically bonded phase packing materials for High performance liquid chromatography (HPLC were obtained using spectra obtained by solid state cross-polarization (CP magic-angle spinning (MAS nuclear magnetic resonance (NMR spectroscopic experiments for the 29Si, and 13C nuclei. These packing materials were: Cogent bidentate C18 bonded to type-C silica, hybrid packing materials XTerra MS C18, and XBridge Prep. C18. The spectra obtained using cross-polarization magic angle spinning (CP-MAS on the Cogent bidentate C18 bonded to type-C silica show the surface to be densely populated with hydride groups (Si-H, with a relative surface coverage exceeding 80%. The hybrid packing materials XTerra and XBridge gave spectra that reveal the silicon atoms to be bonded to organic moieties embedded in the molecular structure of these materials with over 90% of the alkyl silicon atoms found within the completely condensed silicon environments. The hydrolytic stability of these materials were investigated in acidic aqueous solutions at pHs of 7.0 and 3.0, and it was found that while the samples of XTerra and XBridge were not affected by hydrolysis at this pH range, the sample of Cogent lost a significant proportion of its Si-H groups after five days of treatment in acidic aqueous solution.

Active screen plasma nitriding enhances cell attachment to polymer surfaces

International Nuclear Information System (INIS)

Kaklamani, Georgia; Bowen, James; Mehrban, Nazia; Dong, Hanshan; Grover, Liam M.; Stamboulis, Artemis

2013-01-01

Active screen plasma nitriding (ASPN) is a well-established technique used for the surface modification of materials, the result of which is often a product with enhanced functional performance. Here we report the modification of the chemical and mechanical properties of ultra-high molecular weight poly(ethylene) (UHMWPE) using 80:20 (v/v) N 2 /H 2 ASPN, followed by growth of 3T3 fibroblasts on the treated and untreated polymer surfaces. ASPN-treated UHMWPE showed extensive fibroblast attachment within 3 h of seeding, whereas fibroblasts did not successfully attach to untreated UHMWPE. Fibroblast-coated surfaces were maintained for up to 28 days, monitoring their metabolic activity and morphology throughout. The chemical properties of the ASPN-treated UHMWPE surface were studied using X-ray photoelectron spectroscopy, revealing the presence of C-N, C=N, and C≡N chemical bonds. The elastic modulus, surface topography, and adhesion properties of the ASPN-treated UHMWPE surface were studied over 28 days during sample storage under ambient conditions and during immersion in two commonly used cell culture media.

COMPOSITE RESIN BOND STRENGTH TO ETCHED DENTINWITH ONE SELF PRIMING ADHESIVE

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P SAMIMI

2002-09-01

Full Text Available Introduction. The purpose of this study was to compare shear bond strength of composite resins to etched dentin in both dry and wet dentin surface with active and inactive application of a single-bottle adhesive resin (Single Bond, 3M Dental products. Methods. Fourthy four intact human extracted molars and premolars teeth were selected. The facial surfaces of the teeth were grounded with diamond bur to expose dentin. Then specimens were divided into four groups of 11 numbers (9 Molars and 2 Premolars. All the samples were etched with Phosphoric Acid Gel 35% and then rinsed for 10 seconds. The following stages were carried out for each group: Group I (Active-Dry: After rinsing, air drying of dentin surface for 15 seconds, active priming of adhesive resin for 15 seconds, air drying for 5 seconds, the adhesive resin layer was light cured for 10 seconds. Group III (Inactive-Dry:After rinsing, air drying of dentin surface for 15 seconds, adhesive resin was applied and air dryied for 5 seconds, the adhesive layer was light cured for 10 seconds. Group III (Active-Wet:After rinsing, removal of excess water of dentin surface with a cotton roll, active priming of adhesive resin for 15 seconds and air drying for 5 seconds, the adhesive layer was light cured for 10 seconds. Group IV (Inactive-Wet:After rinsing, removal of excess water of dentin surface with a cotton roll, the adhesive resin was applied and air dryied for 5 seconds and then cured for 10 seconds. After adhesive resin application, composite resin (Z250, 3M Dental products was applied on prepared surface with cylindrical molds (with internal diameter of 2.8mm, & height of 5mm and light-cured for 100 seconds (5x20s. The samples were then thermocycled. They were located in 6±3c water .temperature for 10 seconds and then 15 seconds in inviromental temperature, 10s in 55±3c water temperature and then were located at room temperature for 15s. This test was repeated for 100s. All of the specimens

One-step surface modification for irreversible bonding of various plastics with a poly(dimethylsiloxane) elastomer at room temperature.

Science.gov (United States)

Wu, Jing; Lee, Nae Yoon

2014-05-07

Here, we introduce a simple and facile method for bonding poly(dimethylsiloxane) (PDMS) to various plastics irreversibly via a one-step chemical treatment at room temperature. This was mediated by poly[dimethylsiloxane-co-(3-aminopropyl)methylsiloxane] (amine-PDMS linker), a chemical composed of a PDMS backbone incorporating an amine side group. Room temperature anchoring of the linker was achieved via a reaction between the amine functionality of the linker and the carbon backbone of the plastics, thereby producing urethane bonds. This resulted in the PDMS functionality being exposed on the plastic surface, mimicking the surface properties of bulk PDMS. Following corona treatment of the PDMS-modified plastic and a sheet of PDMS, the two surfaces were placed in contact with each other and heated at 80 °C for 1 h. This resulted in permanent bonding between PDMS and the plastic. To examine the effectiveness of the amine-PDMS linker coating procedure, the surfaces were characterized by measuring water contact angles and by employing X-ray photoelectron spectroscopy (XPS). Polycarbonate (PC), poly(ethylene terephthalate) (PET), poly(vinylchloride) (PVC), and polyimide (PI) were bonded successfully to PDMS using this method, with bond strengths of PC, PET, and PVC with PDMS measured to be approximately 428.5 ± 17.9, 361.7 ± 31.2, and 430.0 ± 14.9 kPa, respectively. The bond strength of a PC-PC homogeneous assembly, also realized using the proposed method, was measured to be approximately 343.9 ± 7.4 kPa. Delamination tests revealed that the PC-PC assembly was able to withstand intense introduction of a liquid whose per-minute injection volume was approximately 278 times greater than the total internal volume of the microchannel fabricated in PC. This demonstrated the robustness of the seal formed using the proposed technique.

Effect of surface treatment and type of cement on push-out bond strength of zirconium oxide posts.

Science.gov (United States)

Almufleh, Balqees S; Aleisa, Khalil I; Morgano, Steven M

2014-10-01

The effect of the surface treatment of zirconium oxide posts on their push-out bond strength is controversial. The purpose of this study was to compare the effects of 2 surface treatments on the bond strength of zirconium oxide posts cemented with different cements and to assess the failure mode. Seventy extracted human teeth were divided into 7 groups (n=10). Custom zirconium oxide posts (Cercon; Degudent) were fabricated for 6 groups. Posts in 3 groups were airborne-particle abraded (A). Posts in the other 3 groups were tribochemical silica coated (T). Three cements were used. Zinc phosphate cement was used to cement the zirconium oxide posts in groups AZ and TZ, RelyX ARC cement was used in groups ARA and TRA, and RelyX Unicem cement was used in groups ARU and TRU. Group C contained custom metal posts cemented with zinc phosphate cement. Specimens were horizontally sectioned into 3 sections and subjected to a push-out test. A mixed model analysis of variance, 1-way ANOVA, and the Tukey multiple comparison tests were used for statistical analysis. The highest push-out bond strength was recorded for Group ARU (21.03 MPa), and the lowest was recorded for Group ARA (7.57 MPa). No significant difference in push-out bond strength was found among the different surface treatments and root regions (P>.05). The type of cement had a significant effect on the push-out bond strength of zirconium oxide posts (P=.049). RelyX Unicem cement recorded (19.57 ±8.83 MPa) significantly higher push-out bond strength compared with zinc phosphate (9.95 ±6.31 MPa) and RelyX ARC cements (9.39 ±5.45 MPa). Adhesive failure at the post-cement interface was recorded for 75% of the posts cemented with zinc phosphate and RelyX ARC cements, while mixed failure was recorded for 75% of the posts cemented with RelyX Unicem cement. The type of cement used resulted in a statistically significant difference in the push-out bond strength of zirconium oxide posts, while both the surface treatment

B-H Bond Activation by an Amidinate-Stabilized Amidosilylene: Non-Innocent Amidinate Ligand.

Science.gov (United States)

Khoo, Sabrina; Shan, Yu-Liang; Yang, Ming-Chung; Li, Yongxin; Su, Ming-Der; So, Cheuk-Wai

2018-05-21

The activation of B-H and B-Cl bonds in boranes by base-stabilized low-valent silicon compounds is described. The reaction of the amidinato amidosilylene-borane adduct [L{Ar(Me 3 Si)N}SiBH 3 ] [1; L = PhC(N tBu) 2 , and Ar = 2,6- iPr 2 C 6 H 3 ] with MeOTf in toluene at room temperature formed [L{Ar(Me 3 Si)N}SiBH 2 OTf] (2). [LSiN(SiMe 3 )Ar] in compound 2 then underwent a B-H bond activation with BH 2 OTf in refluxing toluene to afford the B-H bond activation product [LB(H)Si(H)(OTf){N(SiMe 3 )Ar}] (3). On the other hand, when compound 2 was reacted with 4-dimethylaminopyridine in refluxing toluene, another B-H bond activation product [(μ-κ1:κ1-L)B(H)(DMAP)Si(H){N(Ar)SiMe 3 }]OTf (4) was afforded. Mechanistic studies show that "(μ-κ1:κ1-L)B(H)(OTf)Si(H){N(Ar)SiMe 3 }" (2A) is the key intermediate in the reactions mentioned above. The formation of 2A is further evidenced by the activation of the B-Cl bond in PhBCl 2 by the amidinato silicon(I) dimer [LSi:] 2 to form the B-Cl bond activation product [(μ-κ1:κ1-L)B(Cl)(Ph)Si(Cl)] 2 (6). Compounds 2-4 and 6 were characterized by nuclear magnetic resonance spectroscopy and X-ray crystallography.

Comparative evaluation of tensile bond strength of silicone-based denture liners after thermocycling and surface treatment

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Harsimran Kaur

2015-01-01

Full Text Available Purpose: To examine, evaluate, and compare the tensile bond strength of two silicone-based liners; one autopolymerizing and one heat cured, when treated with different chemical etchants to improve their adhesion with denture base resin. Materials and Methods: Hundred and sixty test specimens of heat-cured polymethyl methacrylate (PMMA were fabricated; out of which 80 specimens were tested for tensile bond strength after bonding it to autopolymerizing resilient liner (Ufigel P and rest 80 to heat-cured resilient liner (Molloplast B. Each main group was further divided into four subgroups of 20 specimens each, one to act as a control and three were subjected to surface treatment with different chemical etchants namely dichloromethane, MMA monomer, and chloroform. The two silicone-based denture liners were processed between 2 PMMA specimens (10 mm × 10 mm × 40 mm in the space provided by a spacer of 3 mm, thermocycled (5-55°C for 500 cycles, and then their tensile strength measurements were done in the universal testing machine. Results: One-way ANOVA technique showed a highly significant difference in the mean tensile bond strength values for all the groups. The Student′s t-test computed values of statistics for the compared groups were greater than the critical values both at 5% and at 1% levels. Conclusion: Surface treatment of denture base resin with chemical etchants prior to the application of silicone-based liner (Ufigel P and Molloplast-B increased the tensile bond strength. The increase was the highest with specimens subjected to 180 s of MMA surface treatment and the lowest with control group specimens.

[Effect of hydrofluoric acid concentration on the surface morphology and bonding effectiveness of lithium disilicate glass ceramics to resin composites].

Science.gov (United States)

Hailan, Qian; Lingyan, Ren; Rongrong, Nie; Xiangfeng, Meng

2017-12-01

This study aimed at determining the influence of hydrofluoric acid (HF) in varied concentrations on the surface morphology of lithium disilicate glass ceramics and bond durability between resin composites and post-treated lithium disilicate glass ceramics. After being sintered, ground, and washed, 72 as-prepared specimens of lithium disilicate glass ceramics with dimensions of 11 mm×13 mm×2 mm were randomly divided into three groups. Each group was treated with acid solution [32% phosphoric acid (PA) or 4% or 9.5% HF] for 20 s. Then, four acidified specimens from each group were randomly selected. One of the specimens was used to observe the surface morphology using scanning electron microscopy, and the others were used to observe the surface roughness using a surface roughness meter (including Ra, Rz, and Rmax). After treatment with different acid solutions in each group, 20 samples were further treated with silane coupling agent/resin adhesive/resin cement (Monobond S/Multilink Primer A&B/Multilink N), followed by bonding to a composite resin column (Filtek™ Z350) with a diameter of 3 mm. A total of 20 specimens in each group were randomly divided into two subgroups, which were used for measuring the microshear bond strength, with one of them subjected to cool-thermal cycle for 20 000 times. The surface roughness (Ra, Rz, and Rmax) of lithium disilicate glass ceramics treated with 4% or 9.5% HF was significantly higher than that of the ceramic treated with PA (Pglass ceramics treated with 9.5% HF also demonstrated better surface roughness (Rz and Rmax) than that of the ceramics treated with 4% HF. Cool-thermal cycle treatment reduced the bond strength of lithium disilicate glass ceramics in all groups (Pglass ceramics treated with HF had higher bond strength than that of the ceramics treated with PA. The lithium disilicate glass ceramics treated with 4% HF had higher bond strength than that of the ceramics treated with 9.5% HF (Pglass ceramics treated with 4

Cold pressure welding - the mechanisms governing bonding

DEFF Research Database (Denmark)

Bay, Niels

1979-01-01

Investigations of the bonding surface in scanning electron microscope after fracture confirm the mechanisms of bond formation in cold pressure welding to be: fracture of work-hardened surface layer, surface expansion increasing the area of virgin surface, extrusion of virgin material through cracks...... of the original surface layer, and establishment of real contact and bonding between virgin material. This implies that normal pressure as well as surface expansion are basic parameters governing the bond strength. Experimental investigations of pressure welding Al-Al under plane strain compression in a specially...

Fabrication and Characterization of Capacitive Micromachined Ultrasonic Transducers with Low-Temperature Wafer Direct Bonding

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Xiaoqing Wang

2016-12-01

Full Text Available This paper presents a fabrication method of capacitive micromachined ultrasonic transducers (CMUTs by wafer direct bonding, which utilizes both the wet chemical and O2plasma activation processes to decrease the bonding temperature to 400 °C. Two key surface properties, the contact angle and surface roughness, are studied in relation to the activation processes, respectively. By optimizing the surface activation parameters, a surface roughness of 0.274 nm and a contact angle of 0° are achieved. The infrared images and static deflection of devices are assessed to prove the good bonding effect. CMUTs having silicon membranes with a radius of 60 μm and a thickness of 2 μm are fabricated. Device properties have been characterized by electrical and acoustic measurements to verify their functionality and thus to validate this low-temperature process. A resonant frequency of 2.06 MHz is obtained by the frequency response measurements. The electrical insertion loss and acoustic signal have been evaluated. This study demonstrates that the CMUT devices can be fabricated by low-temperature wafer direct bonding, which makes it possible to integrate them directly on top of integrated circuit (IC substrates.

Effect of alloy type and surface conditioning on roughness and bond strength of metal brackets

NARCIS (Netherlands)

Nergiz, I.; Schmage, P.; Herrmann, W.; Ozcan, M.; Nergiz, [No Value

2004-01-01

The effect of 5 different surface conditioning methods on bonding of metal brackets to cast dental alloys was examined. The surface conditioning methods were fine (30-µm) or rough (125-µm) diamond bur, sandblasting (50-µm or 110-µm aluminum oxide [Al2O3]), and silica coating (30-µm silica). Fifty

Shear Bond Strength of Three Orthodontic Bonding Systems on Enamel and Restorative Materials

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Andreas Hellak

2016-01-01

Full Text Available Objective. The aim of this in vitro study was to determine the shear bond strength (SBS and adhesive remnant index (ARI score of two self-etching no-mix adhesives (iBond™ and Scotchbond™ on different prosthetic surfaces and enamel, in comparison with the commonly used total etch system Transbond XT™. Materials and Methods. A total of 270 surfaces (1 enamel and 8 restorative surfaces, n=30 were randomly divided into three adhesive groups. In group 1 (control brackets were bonded with Transbond XT primer. In the experimental groups iBond adhesive (group 2 and Scotchbond Universal adhesive (group 3 were used. The SBS was measured using a Zwicki 1120™ testing machine. The ARI and SBS were compared statistically using the Kruskal–Wallis test (P≤0.05. Results. Significant differences in SBS and ARI were found between the control group and experimental groups. Conclusions. Transbond XT showed the highest SBS on human enamel. Scotchbond Universal on average provides the best bonding on all other types of surface (metal, composite, and porcelain, with no need for additional primers. It might therefore be helpful for simplifying bonding in orthodontic procedures on restorative materials in patients. If metal brackets have to be bonded to a metal surface, the use of a dual-curing resin is recommended.

Influence of Pre-Sintered Zirconia Surface Conditioning on Shear Bond Strength to Resin Cement

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Tomofumi Sawada

2016-06-01

Full Text Available This study analyzed the shear bond strength (SBS of resin composite on zirconia surface to which a specific conditioner was applied before sintering. After sintering of either conditioner-coated or uncoated specimens, both groups were divided into three subgroups by their respective surface modifications (n = 10 per group: no further treatment; etched with hydrofluoric acid; and sandblasted with 50 µm Al2O3 particles. Surfaces were characterized by measuring different surface roughness parameters (e.g., Ra and Rmax and water contact angles. Half of the specimens underwent thermocycling (10,000 cycles, 5–55 °C after self-adhesive resin cement build-up. The SBSs were measured using a universal testing machine, and the failure modes were analyzed by microscopy. Data were analyzed by nonparametric and parametric tests followed by post-hoc comparisons (α = 0.05. Conditioner-coated specimens increased both surface roughness and hydrophilicity (p < 0.01. In the non-thermocycled condition, sandblasted surfaces showed higher SBSs than other modifications, irrespective of conditioner application (p < 0.05. Adhesive fractures were commonly observed in the specimens. Thermocycling favored debonding and decreased SBSs. However, conditioner-coated specimens upon sandblasting showed the highest SBS (p < 0.05 and mixed fractures were partially observed. The combination of conditioner application before sintering and sandblasting after sintering showed the highest shear bond strength and indicated improvements concerning the failure mode.

Discrete impurity band from surface danging bonds in nitrogen and phosphorus doped SiC nanowires

Science.gov (United States)

Li, Yan-Jing; Li, Shu-Long; Gong, Pei; Li, Ya-Lin; Cao, Mao-Sheng; Fang, Xiao-Yong

2018-04-01

The electronic structure and optical properties of the nitrogen and phosphorus doped silicon carbide nanowires (SiCNWs) are investigated using first-principle calculations based on density functional theory. The results show doping can change the type of the band gap and improve the conductivity. However, the doped SiCNWs form a discrete impurity levels at the Fermi energy, and the dispersion degree decreases with the diameter increasing. In order to reveal the root of this phenomenon, we hydrogenated the doped SiCNWs, found that the surface dangling bonds were saturated, and the discrete impurity levels are degeneracy, which indicates that the discrete impurity band of the doped SiCNWs is derived from the dangling bonds. The surface passivation can degenerate the impurity levels. Therefore, both doping and surface passivation can better improve the photoelectric properties of the SiCNWs. The result can provide additional candidates in producing nano-optoelectronic devices.

Development of reconstitution method for surveillance specimens using surface activated joining

Energy Technology Data Exchange (ETDEWEB)

Nakamura, Terumi; Kaihara, Shoichiro; Yoshida, Kazuo; Sato, Akira [Ishikawajima-Harima Heavy Industries Co. Ltd., Tokyo (Japan); Onizawa, Kunio; Nishiyama, Yutaka; Fukaya, Kiyoshi; Suzuki, Masahide

1996-03-01

Evaluation of embrittlement of reactor vessel steel due to irradiation requires surveillance tests. However, many surveillance specimens are necessary for nuclear plants life extension. Therefore, a specimen reconstitution technique has become important to provide the many specimens for continued surveillance. A surface activated joining (SAJ) method has been developed to join various materials together at low temperatures with little deformation, and is useful to bond irradiated specimens. To assess the validity of this method, Charpy impact tests were carried out, and the characteristics caused by heating during joining were measured. The test results showed the Charpy impact values were almost the same as base materials, and surface activated joining reduced heat affected zone to less than 2 mm. (author).

New approaches to organocatalysis based on C–H and C–X bonding for electrophilic substrate activation

Directory of Open Access Journals (Sweden)

Pavel Nagorny

2016-12-01

Full Text Available Hydrogen bond donor catalysis represents a rapidly growing subfield of organocatalysis. While traditional hydrogen bond donors containing N–H and O–H moieties have been effectively used for electrophile activation, activation based on other types of non-covalent interactions is less common. This mini review highlights recent progress in developing and exploring new organic catalysts for electrophile activation through the formation of C–H hydrogen bonds and C–X halogen bonds.

Surface/subsurface observation and removal mechanisms of ground reaction bonded silicon carbide

Science.gov (United States)

Yao, Wang; Zhang, Yu-Min; Han, Jie-cai; Zhang, Yun-long; Zhang, Jian-han; Zhou, Yu-feng; Han, Yuan-yuan

2006-01-01

Reaction Bonded Silicon Carbide (RBSiC) has long been recognized as a promising material for optical applications because of its unique combination of favorable properties and low-cost fabrication. Grinding of silicon carbide is difficult because of its high hardness and brittleness. Grinding often induces surface and subsurface damage, residual stress and other types of damage, which have great influence on the ceramic components for optical application. In this paper, surface integrity, subsurface damage and material removal mechanisms of RBSiC ground using diamond grinding wheel on creep-feed surface grinding machine are investigated. The surface and subsurface are studied with scanning electron microscopy (SEM) and optical microscopy. The effects of grinding conditions on surface and subsurface damage are discussed. This research links the surface roughness, surface and subsurface cracks to grinding parameters and provides valuable insights into the material removal mechanism and the dependence of grind induced damage on grinding conditions.

Diffusion bonding

International Nuclear Information System (INIS)

Anderson, R.C.

1976-01-01

A method is described for joining beryllium to beryllium by diffusion bonding. At least one surface portion of at least two beryllium pieces is coated with nickel. A coated surface portion is positioned in a contiguous relationship with another surface portion and subjected to an environment having an atmosphere at a pressure lower than ambient pressure. A force is applied on the beryllium pieces for causing the contiguous surface portions to abut against each other. The contiguous surface portions are heated to a maximum temperature less than the melting temperature of the beryllium, and the applied force is decreased while increasing the temperature after attaining a temperature substantially above room temperature. A portion of the applied force is maintained at a temperature corresponding to about maximum temperature for a duration sufficient to effect the diffusion bond between the contiguous surface portions

The interplay between surface-water and hydrogen bonding in a water adlayer on Pt(111) and Ag(111)

Energy Technology Data Exchange (ETDEWEB)

Delle Site, Luigi [Max-Planck-Institut fuer Polymerforschung, Ackermannweg 10, D-55128 Mainz (Germany); Ghiringhelli, Luca M [Max-Planck-Institut fuer Polymerforschung, Ackermannweg 10, D-55128 Mainz (Germany); Andreussi, Oliviero [Scuola Normale Superiore, Piazza dei Cavalieri 7, 56100 Pisa (Italy); Donadio, Davide [Computational Science, Department of Chemistry and Applied Biosciences, ETH Zurich, USI-Campus, via Giuseppe Buffi 13, CH-6900 Lugano (Switzerland); Parrinello, Michele [Scuola Normale Superiore, Piazza dei Cavalieri 7, 56100 Pisa (Italy)

2007-06-20

The structure of a water adlayer on a Pt(111) surface is investigated by means of extensive first-principles calculations. Allowing for proton disorder, the ground state energy for the {radical}3 x {radical}3R30{sup o} structure can be found. This results from an interplay between water/metal chemical bonding and the hydrogen bonding of the water network. This picture is supported by substituting Pt(111) with Ag(111): the almost inert surface allows for the reconstruction of the hydrogen network. (fast track communication)

The interplay between surface-water and hydrogen bonding in a water adlayer on Pt(111) and Ag(111)

International Nuclear Information System (INIS)

Delle Site, Luigi; Ghiringhelli, Luca M; Andreussi, Oliviero; Donadio, Davide; Parrinello, Michele

2007-01-01

The structure of a water adlayer on a Pt(111) surface is investigated by means of extensive first-principles calculations. Allowing for proton disorder, the ground state energy for the √3 x √3R30 o structure can be found. This results from an interplay between water/metal chemical bonding and the hydrogen bonding of the water network. This picture is supported by substituting Pt(111) with Ag(111): the almost inert surface allows for the reconstruction of the hydrogen network. (fast track communication)

Influence of warm air-drying on enamel bond strength and surface free-energy of self-etch adhesives.

Science.gov (United States)

Shiratsuchi, Koji; Tsujimoto, Akimasa; Takamizawa, Toshiki; Furuichi, Tetsuya; Tsubota, Keishi; Kurokawa, Hiroyasu; Miyazaki, Masashi

2013-08-01

We examined the effect of warm air-drying on the enamel bond strengths and the surface free-energy of three single-step self-etch adhesives. Bovine mandibular incisors were mounted in self-curing resin and then wet ground with #600 silicon carbide (SiC) paper. The adhesives were applied according to the instructions of the respective manufacturers and then dried in a stream of normal (23°C) or warm (37°C) air for 5, 10, and 20 s. After visible-light irradiation of the adhesives, resin composites were condensed into a mold and polymerized. Ten samples per test group were stored in distilled water at 37°C for 24 h and then the bond strengths were measured. The surface free-energies were determined by measuring the contact angles of three test liquids placed on the cured adhesives. The enamel bond strengths varied according to the air-drying time and ranged from 15.8 to 19.1 MPa. The trends for the bond strengths were different among the materials. The value of the γS⁺ component increased slightly when drying was performed with a stream of warm air, whereas that of the γS⁻ component decreased significantly. These data suggest that warm air-drying is essential to obtain adequate enamel bond strengths, although increasing the drying time did not significantly influence the bond strength. © 2013 Eur J Oral Sci.

Shear bond strength of resin composite bonded with two adhesives: Influence of Er: YAG laser irradiation distance

Science.gov (United States)

Shirani, Farzaneh; Birang, Reza; Malekipour, Mohammad Reza; Hourmehr, Zahra; Kazemi, Shantia

2014-01-01

Background: Dental surfaces prepared with different Er:YAG laser distance may have different characteristics compared with those prepared with conventional instruments. The aim of this study was to investigate the effect of Er:YAG laser irradiation distance from enamel and dentin surfaces on the shear bond strength of composite with self-etch and etch and rinse bonding systems compared with conventional preparation method. Materials and Methods: Two hundred caries-free human third molars were randomly divided into twenty groups (n = 10). Ten groups were designated for enamel surface (E1-E10) and ten for dentin surface (D1-D10). Er: YAG laser (2940 nm) was used on the E1-E8 (240 mJ, 25 Hz) and D1-D8 (140 mJ, 30 Hz) groups at four different distances of 0.5 (standard), 2, 4 and 11 mm. Control groups (E9, E10, D9 and D10) were ground with medium grit diamond bur. The enamel and dentin specimens were divided into two subgroups that were bonded with either Single Bond or Clearfil SE Bond. Resin composite (Z100) was dispensed on prepared dentin and enamel. The shear bond strengths were tested using a universal testing machine. Data were analyzed by SPSS12 statistical software using three way analysis of variance, Tukey and independent t-test. P enamel and dentin substrates (P enamel surfaces (in both bonding agent subgroups) and on dentin surfaces (in the Single Bond subgroup). Conclusion: Laser irradiation decreases shear bond strength. Irradiation distance affects shear bond strength and increasing the distance would decrease the negative effects of laser irradiation. PMID:25540665

26 CFR 1.103(n)-1T - Limitation on aggregrate amount of private activity bonds (temporary).

Science.gov (United States)

2010-04-01

... activity bonds (temporary). 1.103(n)-1T Section 1.103(n)-1T Internal Revenue INTERNAL REVENUE SERVICE... Excluded from Gross Income § 1.103(n)-1T Limitation on aggregrate amount of private activity bonds (temporary). Q-1: What does section 103(n) provide? A-1: Interest on an issue of private activity bonds will...

A General Catalyst for Site-Selective C(sp(3))-H Bond Amination of Activated Secondary over Tertiary Alkyl C(sp(3))-H Bonds.

Science.gov (United States)

Scamp, Ryan J; Jirak, James G; Dolan, Nicholas S; Guzei, Ilia A; Schomaker, Jennifer M

2016-06-17

The discovery of transition metal complexes capable of promoting general, catalyst-controlled and selective carbon-hydrogen (C-H) bond amination of activated secondary C-H bonds over tertiary alkyl C(sp(3))-H bonds is challenging, as substrate control often dominates when reactive nitrene intermediates are involved. In this letter, we report the design of a new silver complex, [(Py5Me2)AgOTf]2, that displays general and good-to-excellent selectivity for nitrene insertion into propargylic, benzylic, and allylic C-H bonds over tertiary alkyl C(sp(3))-H bonds.

bond activation and catalysis by Ru -pac complexes

Indian Academy of Sciences (India)

and their reactivity towards oxidation of a few organic compounds. Keywords. Kinetics; catalysis; -O–O- bond activation; Ru-pac complex; oxidation. 1. Introduction. Ru-pac complexes exhibit catalytic properties,1 in homogeneous conditions in the presence of oxygen atom donors, that mimic the biological enzymatic oxi-.

Effects of ultraviolet irradiation on bonding strength between Co-Cr alloy and citric acid-crosslinked gelatin matrix.

Science.gov (United States)

Inoue, Motoki; Sasaki, Makoto; Katada, Yasuyuki; Taguchi, Tetsushi

2014-02-01

Novel techniques for creating a strong bond between polymeric matrices and biometals are required. We immobilized polymeric matrices on the surface of biometal for drug-eluting stents through covalent bond. We performed to improve the bonding strength between a cobalt-chromium alloy and a citric acid-crosslinked gelatin matrix by ultraviolet irradiation on the surface of cobalt-chromium alloy. The ultraviolet irradiation effectively generated hydroxyl groups on the surface of the alloy. The bonding strength between the gelatin matrix and the alloy before ultraviolet irradiation was 0.38 ± 0.02 MPa, whereas it increased to 0.48 ± 0.02 MPa after ultraviolet irradiation. Surface analysis showed that the citric acid derivatives occurred on the surface of the cobalt-chromium alloy through ester bond. Therefore, ester bond formation between the citric acid derivatives active esters and the hydroxyl groups on the cobalt-chromium alloy contributed to the enhanced bonding strength. Ultraviolet irradiation and subsequent immobilization of a gelatin matrix using citric acid derivatives is thus an effective way to functionalize biometal surfaces.

Hydrogenation of nitriles on a well-characterized nickel surface: From surface science studies to liquid phase catalytic activity measurements

Energy Technology Data Exchange (ETDEWEB)

Gardin, Denis Emmanuel [Univ. of California, Berkeley, CA (United States)

1993-12-01

Nitrile hydrogenation is the most commonly used method for preparing diverse amines. This thesis is aimed at the mechanism and factors affecting the performance of Ni-based catalysts in nitrile hydrogenations. Surface science techniques are used to study bonding of nitriles and amines to a Ni(111) surface and to identify surface intermediates. Liquid-phase hydrogenations of cyclohexene and 1-hexene on a Pt foil were carried out successfully. Finally, knowledge about the surface structure, surface chemical bond, dynamics of surface atoms (diffusion, growth), and reactivity of metal surfaces from solid-gas interface studies, is discussed.

In vitro evaluation of repair bond strength of composite: Effect of surface treatments with bur and laser and application of universal adhesive.

Science.gov (United States)

Kiomarsi, Nazanin; Espahbodi, Melika; Chiniforush, Nasim; Karazifard, Mohammad Javd; Kamangar, Sedighe Sadat Hashemi

2017-09-30

This study aimed to assess the effect of surface treatment by bur and laser and application of universal adhesive on repair bond strength of composite resin. A total of 120 composite blocks measuring 6×4×4 mm were fabricated of Filtek Z250 composite. All samples were subjected to 5,000 thermal cycles and divided into two groups for surface preparation by bur and by Er,Cr:YSGG laser (n = 60). The surfaces were then etched with orthophosphoric acid, rinsed with water and divided into three groups (silane, silane plus Single Bond and silane plus Single Bond Universal). Repair composite was then bonded to aged composite. Half of the samples in each group were stored in distilled water at 37°C for 24 hours and the other half underwent 5000 thermal cycles. All samples were then subjected to shear bond strength testing using a universal testing machine at a crosshead speed of 1 mm/minute. The data were analyzed using one-way ANOVA and Tukey's HSD test. Mode of failure was determined using a stereomicroscope. Bur preparation plus universal adhesive yielded the highest bond strength (30.16 µ 2.26 MPa). Laser plus silane yielded the lowest bond strength (5.63 µ 2.43 MPa). Bur preparation yielded significantly higher bond strength than laser (P composite by bur and application of universal adhesive can improve the repair bond strength of composite. Application of silane (without adhesive) in the process of repair cannot provide adequately high repair bond strength.

Determination of Optimal Parameters for Diffusion Bonding of Semi-Solid Casting Aluminium Alloy by Response Surface Methodology

Directory of Open Access Journals (Sweden)

Kaewploy Somsak

2015-01-01

Full Text Available Liquid state welding techniques available are prone to gas porosity problems. To avoid this solid state bonding is usually an alternative of preference. Among solid state bonding techniques, diffusion bonding is often employed in aluminium alloy automotive parts welding in order to enhance their mechanical properties. However, there has been no standard procedure nor has there been any definitive criterion for judicious welding parameters setting. It is thus a matter of importance to find the set of optimal parameters for effective diffusion bonding. This work proposes the use of response surface methodology in determining such a set of optimal parameters. Response surface methodology is more efficient in dealing with complex process compared with other techniques available. There are two variations of response surface methodology. The one adopted in this work is the central composite design approach. This is because when the initial upper and lower bounds of the desired parameters are exceeded the central composite design approach is still capable of yielding the optimal values of the parameters that appear to be out of the initially preset range. Results from the experiments show that the pressing pressure and the holding time affect the tensile strength of jointing. The data obtained from the experiment fits well to a quadratic equation with high coefficient of determination (R2 = 94.21%. It is found that the optimal parameters in the process of jointing semi-solid casting aluminium alloy by using diffusion bonding are the pressing pressure of 2.06 MPa and 214 minutes of the holding time in order to achieve the highest tensile strength of 142.65 MPa

Modification of Purine and Pyrimidine Nucleosides by Direct C-H Bond Activation

Directory of Open Access Journals (Sweden)

Yong Liang

2015-03-01

Full Text Available Transition metal-catalyzed modifications of the activated heterocyclic bases of nucleosides as well as DNA or RNA fragments employing traditional cross-coupling methods have been well-established in nucleic acid chemistry. This review covers advances in the area of cross-coupling reactions in which nucleosides are functionalized via direct activation of the C8-H bond in purine and the C5-H or C6-H bond in uracil bases. The review focuses on Pd/Cu-catalyzed couplings between unactivated nucleoside bases with aryl halides. It also discusses cross-dehydrogenative arylations and alkenylations as well as other reactions used for modification of nucleoside bases that avoid the use of organometallic precursors and involve direct C-H bond activation in at least one substrate. The scope and efficiency of these coupling reactions along with some mechanistic considerations are discussed.

Evaluation of bond strength between grooved titanium alloy implant abutments and provisional veneering materials after surface treatment of the abutments: An in vitro study

Directory of Open Access Journals (Sweden)

Gowtham Venkat

2017-01-01

Full Text Available Introduction: Titanium has become the material of choice with greater applications in dental implants. The success of the dental implant does not only depend on the integration of the implant to the bone but also on the function and longevity of the superstructure. The clinical condition that demands long-term interim prosthesis is challenging owing to the decreased bond between the abutment and the veneering material. Hence, various surface treatments are done on the abutments to increase the bond strength. Aim: This study aimed to evaluate the bond strength between the abutment and the provisional veneering materials by surface treatments such as acid etching, laser etching, and sand blasting of the abutment. Materials and Methods: Forty titanium alloy abutments of 3 mm diameter and 11 mm height were grouped into four groups with ten samples. Groups A, B, C, and D are untreated abutments, sand blasted with 110 μm aluminum particles, etched with 1% hydrofluoric acid and 30% nitric acid, and laser etched with Nd: YAG laser, respectively. Provisional crowns were fabricated with bis-acrylic resin and cemented with noneugenol temporary luting cement. The shear bond strength was measured in universal testing machine using modified Shell–Nielsen shear test after the cemented samples were stored in water at 25°C for 24 h. Load was applied at a constant cross head speed of 5 mm/min until a sudden decrease in resistance indicative of bond failure was observed. The corresponding force values were recorded, and statistical analysis was done using one-way ANOVA and Newman–Keuls post hoc test. Results: The laser-etched samples showed higher bond strength. Conclusion: Among the three surface treatments, laser etching showed the highest bond strength between titanium alloy implant abutment and provisional restorations. The sand-blasted surfaces demonstrated a significant difference in bond strength compared to laser-etched surfaces. The results of this

Evaluation of Bond Strength between Grooved Titanium Alloy Implant Abutments and Provisional Veneering Materials after Surface Treatment of the Abutments: An In vitro Study.

Science.gov (United States)

Venkat, Gowtham; Krishnan, Murugesan; Srinivasan, Suganya; Balasubramanian, Muthukumar

2017-01-01

Titanium has become the material of choice with greater applications in dental implants. The success of the dental implant does not only depend on the integration of the implant to the bone but also on the function and longevity of the superstructure. The clinical condition that demands long-term interim prosthesis is challenging owing to the decreased bond between the abutment and the veneering material. Hence, various surface treatments are done on the abutments to increase the bond strength. This study aimed to evaluate the bond strength between the abutment and the provisional veneering materials by surface treatments such as acid etching, laser etching, and sand blasting of the abutment. Forty titanium alloy abutments of 3 mm diameter and 11 mm height were grouped into four groups with ten samples. Groups A, B, C, and D are untreated abutments, sand blasted with 110 μm aluminum particles, etched with 1% hydrofluoric acid and 30% nitric acid, and laser etched with Nd: YAG laser, respectively. Provisional crowns were fabricated with bis-acrylic resin and cemented with noneugenol temporary luting cement. The shear bond strength was measured in universal testing machine using modified Shell-Nielsen shear test after the cemented samples were stored in water at 25°C for 24 h. Load was applied at a constant cross head speed of 5 mm/min until a sudden decrease in resistance indicative of bond failure was observed. The corresponding force values were recorded, and statistical analysis was done using one-way ANOVA and Newman-Keuls post hoc test. The laser-etched samples showed higher bond strength. Among the three surface treatments, laser etching showed the highest bond strength between titanium alloy implant abutment and provisional restorations. The sand-blasted surfaces demonstrated a significant difference in bond strength compared to laser-etched surfaces. The results of this study confirmed that a combination of surface treatments and bond agents enhances the

Enamel Wetness Effects on Microshear Bond Strength of Different Bonding Agents (Adhesive Systems): An in vitro Comparative Evaluation Study.

Science.gov (United States)

Kulkarni, Girish; Mishra, Vinay K

2016-05-01

The purpose of this study was to compare the effect of enamel wetness on microshear bond strength using different adhesive systems. To evaluate microshear bond strength of three bonding agents on dry enamel; to evaluate microshear bond strength of three bonding agents on wet enamel; and to compare microshear bond strength of three different bonding agents on dry and wet enamel. Sixty extracted noncarious human premolars were selected for this study. Flat enamel surfaces of approximately 3 mm were obtained by grinding the buccal surfaces of premolars with water-cooled diamond disks. This study evaluated one etch-and-rinse adhesive system (Single Bond 2) and two self-etching adhesive systems (Clearfil SE Bond and Xeno-V). The specimens were divided into two groups (n = 30). Group I (dry) was air-dried for 30 seconds and in group II (wet) surfaces were blotted with absorbent paper to remove excess water. These groups were further divided into six subgroups (n = 10) according to the adhesives used. The resin composite, Filtek Z 250, was bonded to flat enamel surfaces that had been treated with one of the adhesives, following the manufacturer's instructions. After being stored in water at 37°C for 24 hours, bonded specimens were stressed in universal testing machine (Fig. 3) at a crosshead speed of 1 mm/min. The data were evaluated with one-way and two-way analysis of variance (ANOVA), t-test, and Tukey's Multiple Post hoc tests (a = 0.05). The two-way ANOVA and Tukey's Multiple Post hoc tests showed significant differences among adhesive systems, but wetness did not influence microshear bond strength (p = 0.1762). The one-way ANOVA and t-test showed that the all-in-one adhesive (Xeno-V) was the only material influenced by the presence of water on the enamel surface. Xeno-V showed significantly higher microshear bond strength when the enamel was kept wet. Single Bond 2 adhesive showed significantly higher microshear bond strength as compared with Xeno-V adhesive but no

Laser-based surface patterning of composite plates for improved secondary adhesive bonding

KAUST Repository

Tao, Ran

2018-03-01

The effects of laser irradiation surface pretreatments on the mode I fracture toughness of adhesively bonded composite joints were evaluated. First, pulsed CO2 laser irradiation was uniformly deployed on carbon fiber reinforced polymer (CFRP) substrates. Next, double cantilever beam (DCB) tests were performed to assess the effects of surface pretreatments on the mode I fracture toughness of the adhesive joints. Then, a thoughtful combination of the proposed surface pretreatments was deployed to fabricate DCB specimens with patterned interfaces. A wide range of techniques, including X-ray photoelectron spectroscopy (XPS), contact profilometry, and optical and scanning electron microscopy (SEM) were used to ascertain the effects of all investigated surface pretreatments. It is shown that patterning promoted damage mechanisms that were not observed in the uniformly treated interfaces, resulting in an effective fracture toughness well above that predicted by a classical rule of mixture.

Laser-based surface patterning of composite plates for improved secondary adhesive bonding

KAUST Repository

Tao, Ran; Alfano, Marco; Lubineau, Gilles

2018-01-01

The effects of laser irradiation surface pretreatments on the mode I fracture toughness of adhesively bonded composite joints were evaluated. First, pulsed CO2 laser irradiation was uniformly deployed on carbon fiber reinforced polymer (CFRP) substrates. Next, double cantilever beam (DCB) tests were performed to assess the effects of surface pretreatments on the mode I fracture toughness of the adhesive joints. Then, a thoughtful combination of the proposed surface pretreatments was deployed to fabricate DCB specimens with patterned interfaces. A wide range of techniques, including X-ray photoelectron spectroscopy (XPS), contact profilometry, and optical and scanning electron microscopy (SEM) were used to ascertain the effects of all investigated surface pretreatments. It is shown that patterning promoted damage mechanisms that were not observed in the uniformly treated interfaces, resulting in an effective fracture toughness well above that predicted by a classical rule of mixture.

Effect of Surface Treatment, Silane, and Universal Adhesive on Microshear Bond Strength of Nanofilled Composite Repairs.

Science.gov (United States)

Fornazari, I A; Wille, I; Meda, E M; Brum, R T; Souza, E M

 The aim of this study was to evaluate the effect of surface treatment and universal adhesive on the microshear bond strength of nanoparticle composite repairs.  One hundred and forty-four specimens were built with a nanofilled composite (Filtek Supreme Ultra, 3M ESPE). The surfaces of all the specimens were polished with SiC paper and stored in distilled water at 37°C for 14 days. Half of the specimens were then air abraded with Al 2 O 3 particles and cleaned with phosphoric acid. Polished specimens (P) and polished and air-abraded specimens (A), respectively, were randomly divided into two sets of six groups (n=12) according to the following treatments: hydrophobic adhesive only (PH and AH, respectively), silane and hydrophobic adhesive (PCH, ACH), methacryloyloxydecyl dihydrogen phosphate (MDP)-containing silane and hydrophobic adhesive (PMH, AMH), universal adhesive only (PU, AU), silane and universal adhesive (PCU, ACU), and MDP-containing silane and universal adhesive (PMU, AMU). A cylinder with the same composite resin (1.1-mm diameter) was bonded to the treated surfaces to simulate the repair. After 48 hours, the specimens were subjected to microshear testing in a universal testing machine. The failure area was analyzed under an optical microscope at 50× magnification to identify the failure type, and the data were analyzed by three-way analysis of variance and the Games-Howell test (α=0.05).  The variables "surface treatment" and "adhesive" showed statistically significant differences for p<0.05. The highest mean shear bond strength was found in the ACU group but was not statistically different from the means for the other air-abraded groups except AH. All the polished groups except PU showed statistically significant differences compared with the air-abraded groups. The PU group had the highest mean among the polished groups. Cohesive failure was the most frequent failure mode in the air-abraded specimens, while mixed failure was the most common

Comparison of the tensile bond strength of high-noble, noble, and base metal alloys bonded to enamel.

Science.gov (United States)

Sen, D; Nayir, E; Pamuk, S

2000-11-01

Although the bond strengths of various resin composite luting materials have been reported in the literature, the evaluation of these systems with various cast alloys of different compositions has not been completely clarified. To evaluate the tensile bond strength of sandblasted high-noble, noble, and base metal alloys bonded to etched enamel by 2 different bonding agents of different chemical composition: Panavia-Ex (BIS-GMA) and Super-Bond (4-META acrylic). Flat enamel surfaces were prepared on buccal surfaces of 60 extracted noncarious human incisors. Teeth were divided into 3 groups of 20 each. Twenty circular disks of 5 mm diameter were prepared for casting for each group. Group I was cast with a high-noble, group II with a noble, and group III with a base metal alloy. The surfaces of the disks were sandblasted with 250 microm Al(2)O(3). Ten disks of each group were bonded to exposed enamel surfaces with Super-Bond and 10 disks with Panavia-Ex as recommended by the manufacturer. The tensile bond strength was measured with an Instron universal testing machine with a crosshead speed of 0.5 mm/min until failure occurred. Two-way ANOVA was used to evaluate the results. The differences in bond strengths of Super-Bond and Panavia-Ex with different alloys were not significant. The highest bond strengths were obtained in base metal alloys, followed by noble and high-noble alloys. These results were significant. Panavia-Ex and Super-Bond exhibited comparable tensile bond strengths. For both luting agents, the highest bond strengths were achieved with base metal alloys and the lowest with high-noble alloys.

An in vitro comparison of shear bond strength of zirconia to enamel using different surface treatments.

Science.gov (United States)

Zandparsa, Roya; Talua, Nayrouz A; Finkelman, Matthew D; Schaus, Scott E

2014-02-01

The purpose of this in vitro study was to compare the shear bond strength of an airborne-particle abraded zirconia, an acid-etched zirconia (Piranha solution), an Alloy Primer treated zirconia, and a silaned zirconia to enamel, all bonded with a phosphate-methacrylate resin luting agent. Seventy extracted intact human molars were collected, cleaned, and mounted in autopolymerizing acrylic resin, with the experimental surface of the teeth exposed. The specimens were randomly divided into seven groups of zirconia specimens (4 mm diameter, 2 mm thick). Group 1: Airborne-particle abrasion; group 2: Airborne-particle abrasion and Z-PRIME Plus; group 3: Airborne-particle abrasion and alloy primer; group 4: Piranha solution 7:1; group 5: Piranha solution 7:1 and Z-PRIME Plus; group 6: Piranha solution 7:1 and Alloy primer; group 7: CoJet and silane. All specimens were luted with a phosphate-methacrylate resin luting agent (Panavia F2.0) and stored in distilled water for 1 day, then thermocycled (5°C and 55°C) for 500 cycles and tested for shear bond strength (SBS), measured in MPa, with a universal testing machine at a 0.55 mm/min crosshead speed. All specimens were inspected under a scanning electron microscope to determine mode of failure. The mean values and standard deviations of all specimens were calculated for each group. A one-way ANOVA was performed, and multiple pairwise comparisons were then completed with post hoc Tukey test (alpha = 0.05). The airborne-particle abrasion and Z-PRIME Plus group resulted in a significantly higher SBS than the other groups (21.11 ± 6.32 MPa) (p enamel surfaces; however, groups 4, 5, and 6 showed mostly adhesive failures, which left the zirconia surface free of the adhesive materials. No cohesive failures of the substrates (ceramic, resin, or enamel) were observed. Airborne-particle abrasion followed by the application of a zirconia primer produced the highest bond strength to enamel. Therefore, it can be recommended as a

A comparative study of shear bond strength between metal and ceramic brackets and artificially aged composite restorations using different surface treatments.

Science.gov (United States)

Eslamian, Ladan; Borzabadi-Farahani, Ali; Mousavi, Nasim; Ghasemi, Amir

2012-10-01

This in vitro study evaluated the shear bond strength (SBS) between ceramic brackets (CBs) and resin composite restorations (RCRs) prepared using different surface treatments. The findings were also compared with a similar study that used stainless steel brackets (SSBs). Forty-five premolars were restored with a nano-hybrid composite resin (Tetric EvoCeram) and randomly assigned to three surface treatment groups: group 1, 5 per cent hydrofluoric acid (HF); group 2, air abrasion (50 μm alumina particles); and group 3, diamond bur. Specimens were bonded with CBs (Fascination) and exposed to thermo-cycling (500 cycles). The shear force at a crosshead speed of 1 mm/minute was transmitted to brackets. The adhesive remnant index (ARIs) scores were recorded after bracket failure. The analysis of SBS variance (P 0.05) and bond failure occurred mainly in adhesive-bracket base and resin-adhesive interfaces. The diamond bur surface treatment is recommended as a safe and cost-effective method of bonding CBs to RCRs.

Structure determination of the Si(001)-(2 x 1)-H reconstruction by surface X-ray diffraction: Weakening of the dimer bond by the addition of hydrogen

DEFF Research Database (Denmark)

Lauridsen, E.M.; Baker, J.; Nielsen, M.

2000-01-01

The atomic structure of the monohydride Si(001)-(2 x 1)-H reconstruction has been investigated by surface X-ray diffraction. Atomic relaxations down to the eighth layer have been determined. The bond length of the hydrogenated silicon dimers was found to be 2.47 +/- 0.02 Angstrom. which is longer...... than the dimer bond of the clean (2 x 1)-reconstructed Si(001) surface and also 5% longer than the bulk bond length of 2.35 Angstrom. The differences to the (2 x 1) structure of the clean surface are discussed in terms of the elimination of the weak pi-bond character of the dimer bond by the addition...

Effect of surface modifications on the bond strength of zirconia ceramic with resin cement resin.

Science.gov (United States)

Hallmann, Lubica; Ulmer, Peter; Lehmann, Frank; Wille, Sebastian; Polonskyi, Oleksander; Johannes, Martina; Köbel, Stefan; Trottenberg, Thomas; Bornholdt, Sven; Haase, Fabian; Kersten, Holger; Kern, Matthias

2016-05-01

Purpose of this in vitro study was to evaluate the effect of surface modifications on the tensile bond strength between zirconia ceramic and resin. Zirconia ceramic surfaces were treated with 150-μm abrasive alumina particles, 150-μm abrasive zirconia particles, argon-ion bombardment, gas plasma, and piranha solution (H2SO4:H2O2=3:1). In addition, slip casting surfaces were examined. Untreated surfaces were used as the control group. Tensile bond strengths (TBS) were measured after water storage for 3 days or 150 days with additional 37,500 thermal cycling for artificial aging. Statistical analyses were performed with 1-way and 3-way ANOVA, followed by comparison of means with the Tukey HSD test. After storage in distilled water for three days at 37 °C, the highest mean tensile bond strengths (TBS) were observed for zirconia ceramic surfaces abraded with 150-μm abrasive alumina particles (TBS(AAP)=37.3 MPa, TBS(CAAP)=40.4 MPa), and 150-μm abrasive zirconia particles (TBS(AZP)=34.8 MPa, TBS(CAZP)=35.8 MPa). Also a high TBS was observed for specimens treated with argon-ion bombardment (TBS(BAI)=37.8 MPa). After 150 days of storage, specimens abraded with 150-μm abrasive alumina particles and 150-μm abrasive zirconia particles revealed high TBS (TBS(AAP)=37.6 MPa, TBS(CAAP)=33.0 MPa, TBS(AZP)=22.1 MPa and TBS(CAZP)=22.8 MPa). A high TBS was observed also for specimens prepared with slip casting (TBS(SC)=30.0 MPa). A decrease of TBS was observed for control specimens (TBS(UNT)=12.5 MPa, TBS(CUNT)=9.0 MPa), specimens treated with argon-ion bombardment (TBS(BAI)=10.3 MPa) and gas plasma (TBS(GP)=11.0 MPa). A decrease of TBS was observed also for specimens treated with piranha solution (TBS(PS)=3.9 MPa, TBS(CPS)=4.1 MPa). A significant difference in TBS after three days storage was observed for specimens treated with different methods (p0.05), CAAP(p>0.05) and SC(p>0.05). However, the failure patterns of debonded specimens prepared with 150-μm abrasive zirconia

Search for a metallic dangling-bond wire on n-doped H-passivated semiconductor surfaces

DEFF Research Database (Denmark)

Engelund, Mads; Papior, Nick Rübner; Brandimarte, Pedro

2016-01-01

We have theoretically investigated the electronic properties of neutral and n-doped dangling bond (DB) quasi-one-dimensional structures (lines) in the Si(001):H and Ge(001):H substrates with the aim of identifying atomic-scale interconnects exhibiting metallic conduction for use in on-surface cir...

Bond strength of composite resin to enamel: assessment of two ethanol wet-bonding techniques.

Directory of Open Access Journals (Sweden)

Maryam Khoroushi

2014-04-01

Full Text Available Ethanol wet-bonding (EWB technique has been stated to decrease degradation of resin-dentin bond. This study evaluated the effect of two EWB techniques on composite resin-to-enamel bond strength.Silicon carbide papers were used to produce flat enamel surfaces on the buccal faces of forty-five molars. OptiBond FL (OFL adhesive was applied on enamel surfaces in three groups of 15 namely: Enamel surface and OFL (control;Protocol 1 of the EWB technique: absolute ethanol was applied to water-saturated acid-etched enamel surfaces for 1 minute before the application of ethanol-solvated hydrophobic adhesive resin of OFL 3 times;Protocol 2: progressive ethanol replacement; water was gradually removed from the enamel matrix using ascending ethanol concentrations before OFL application. Composite build-ups were made and the specimens were stored for 24 hours at 37°C and 100% relative humidity. Shear bond strength test was performed using a universal testing machine at 1 mm/min crosshead speed. Fracture patterns were evaluated microscopically. Data were analyzed with one-way ANOVA and Fisher's exact test (α=0.05.There were no significant differences in bond strength between the groups (P=0.73. However, regarding failure patterns, the highest cohesive enamel fractures were recorded in groups 2 and 3.In this study, although both methods of EWB did not influence immediate bond strength of composite resin to enamel, the majority of failure patterns occurred cohesively in enamel.

INFLUENCE OF SILANE HEAT TREATMENT ON THE TENSILE BOND STRENGTH BETWEEN EX-3 SYNTHETIC VENEERING PORCELAIN AND COMPOSITE RESIN USING FIVE DIFFERENT ACTIVATION TEMPERATURES

Directory of Open Access Journals (Sweden)

Spartak Yanakiev

2017-02-01

Full Text Available Purpose: The purpose of the present study is to assess the effect of five different silane activation temperatures and eight activation methods on the tensile bond strength between one veneering porcelain and one composite resin material. Material and methods: A total of 81 ceramic rods were made of EX-3 veneering ceramic (Kuraray Noritake Dental, Japan. Sintered ceramic bars were grinded with diamond disks to size 10x2x2mm ± 0,05mm. The front part of each bar was polished. After ultrasonic cleaning in distilled water, the specimens were divided into nine groups. Silane was activated with air at room temperature, 38º С, 50º С, 100º С, 120º С using a custom made blow drier. In a silicone mold, a composite resin Z250 (3М ESPE, St. Paul, USA was condensed toward the bond ceramic surface. A total of 81 specimens approximately 2,0 cm long were prepared for tensile bond testing. One way ANOVA, followed by Bonferroni and Games-Howell tests were used for statistical analysis. Results: The lowest tensile bond strength was observed in the control group (3,51MPa. Group 2 yielded the highest bond strength among all groups (19,54MPa. Silane heat treatment enhanced the bond strength for all treatment methods. Within the polished specimens, the highest bond strength was yielded with warm air at 120ºС (11,31MPa. Conclusion: The most effective method for bonding Z250 composite resin to EX-3 veneering ceramic includes HF etching, silane, and adhesive resin. The most effective heat treatment method for bonding is hot air at 120ºС.

Influence of duration of phosphoric acid pre-etching on bond durability of universal adhesives and surface free-energy characteristics of enamel.

Science.gov (United States)

Tsujimoto, Akimasa; Barkmeier, Wayne W; Takamizawa, Toshiki; Watanabe, Hidehiko; Johnson, William W; Latta, Mark A; Miyazaki, Masashi

2016-08-01

The purpose of this study was to evaluate the influence of duration of phosphoric acid pre-etching on the bond durability of universal adhesives and the surface free-energy characteristics of enamel. Three universal adhesives and extracted human molars were used. Two no-pre-etching groups were prepared: ground enamel; and enamel after ultrasonic cleaning with distilled water for 30 s to remove the smear layer. Four pre-etching groups were prepared: enamel pre-etched with phosphoric acid for 3, 5, 10, and 15 s. Shear bond strength (SBS) values of universal adhesive after no thermal cycling and after 30,000 or 60,000 thermal cycles, and surface free-energy values of enamel surfaces, calculated from contact angle measurements, were determined. The specimens that had been pre-etched showed significantly higher SBS and surface free-energy values than the specimens that had not been pre-etched, regardless of the aging condition and adhesive type. The SBS and surface free-energy values did not increase for pre-etching times of longer than 3 s. There were no significant differences in SBS values and surface free-energy characteristics between the specimens with and without a smear layer. The results of this study suggest that phosphoric acid pre-etching of enamel improves the bond durability of universal adhesives and the surface free-energy characteristics of enamel, but these bonding properties do not increase for phosphoric acid pre-etching times of longer than 3 s. © 2016 Eur J Oral Sci.

Assessment of Bond Strength between Metal Brackets and Non-Glazed Ceramic in Different Surface Treatment Methods

Directory of Open Access Journals (Sweden)

I. Harririan

2010-06-01

Full Text Available Objective: The aim of this study was to evaluate the bond strength between metal brackets and non-glazed ceramic with three different surface treatment methods.Materials and Methods: Forty-two non-glazed ceramic disks were assigned into three groups. Group I and II specimens were etched with 9.5% hydrofluoric acid. Subsequently in group I, silane and adhesive were applied and in group II, bonding agent was used only.In group III, specimens were treated with 35% phosphoric acid and then silane and adhesive were applied. Brackets were bonded with light-cured composites. The specimens were stored in water in room temperature for 24 hours and then thermocycled 500 times between 5°C and 55°C.Results: The difference of tensile bond strength between groups I and III was not significant(P=0.999. However, the tensile bond strength of group II was significantly lower than groups I, and III (P<0.001. The adhesive remnant index scores between the threegroups had statistically significant differences (P<0.001.Conclusion: With the application of scotch bond multi-purpose plus adhesive, we can use phosphoric acid instead of hydrofluoric acid for bonding brackets to non-glazed ceramic restorations.

Shear bond strength of composite bonded with three adhesives to Er,Cr:YSGG laser-prepared enamel.

Science.gov (United States)

Türkmen, Cafer; Sazak-Oveçoğlu, Hesna; Günday, Mahir; Güngör, Gülşad; Durkan, Meral; Oksüz, Mustafa

2010-06-01

To assess in vitro the shear bond strength of a nanohybrid composite resin bonded with three adhesive systems to enamel surfaces prepared with acid and Er,Cr:YSGG laser etching. Sixty extracted caries- and restoration-free human maxillary central incisors were used. The teeth were sectioned 2 mm below the cementoenamel junction. The crowns were embedded in autopolymerizing acrylic resin with the labial surfaces facing up. The labial surfaces were prepared with 0.5-mm reduction to receive composite veneers. Thirty specimens were etched with Er,Cr:YSGG laser. This group was also divided into three subgroups, and the following three bonding systems were then applied on the laser groups and the other three unlased groups: (1) 37% phosphoric acid etch + Bond 1 primer/adhesive (Pentron); (2) Nano-bond self-etch primer (Pentron) + Nano-bond adhesive (Pentron); and (3) all-in-one adhesive-single dose (Futurabond NR, Voco). All of the groups were restored with a nanohybrid composite resin (Smile, Pentron). Shear bond strength was measured with a Zwick universal test device with a knife-edge loading head. The data were analyzed with two-factor ANOVA. There were no significant differences in shear bond strength between self-etch primer + adhesive and all-in-one adhesive systems for nonetched and laser-etched enamel groups (P > .05). However, bond strength values for the laser-etched + Bond 1 primer/adhesive group (48.00 +/- 13.86 MPa) were significantly higher than the 37% phosphoric acid + Bond 1 primer/adhesive group (38.95 +/- 20.07 MPa) (P enamel surface more effectively than 37% phosphoric acid for subsequent attachment of composite material.

Chemial Bond and Stability of Adsorption of[Au(AsS3)]2- on the Surface of Kaolinite

Institute of Scientific and Technical Information of China (English)

MIN Xin-min; CHEN Yun; HONG Han-lie

2004-01-01

Density function theory and discrete variation method (DFT-DVM) were used to study the adsorption of [Au(AsS3 ) ]2- on the surface of kaolinite. The correlation among structure, chemical bond and stability was discussed. Several models were selected with [ Au( AsS3 ) ]2- in different directions and sites. The resultsshow that the models with gold on the edge of kaolinite basal layer contain pincerlike bond among gold and severaloxygen atoms and form strong Au - O covalent bond, so these models are more stable than those with gold aboveor under the layer. The models with gold near to [ AlO2(OH)4 ] octahedra are more stable than those with goldnear to the vacancy without aluminium. These two stable tendencies in kaolinite- [ Au( AsS3 ) ]2- are stronger thanthat in kaolinite-Au systems. The interaction between [ Au( AsS3 ) ]2- and kaolinite is stronger than that betweengold and kaolinite, and this interaction is strong enough to form the surface complexes.

Effects of silica coating and silane surface conditioning on the bond strength of rebonded metal and ceramic brackets

Directory of Open Access Journals (Sweden)

Saadet Atsü

2011-06-01

Full Text Available OBJECTIVE: The aim of this study was to evaluate the effects of tribochemical silica coating and silane surface conditioning on the bond strength of rebonded metal and ceramic brackets. MATERIAL AND METHODS: Twenty debonded metal and 20 debonded ceramic brackets were randomly assigned to receive one of the following surface treatments (n=10 for each group: (1 sandblasting (control; (2 tribochemical silica coating combined with silane. Brackets were rebonded to the enamel surface on the labial and lingual sides of premolars with a light-polymerized resin composite. All specimens were stored in distilled water for 1 week and then thermocycled (5,000 cycles between 5-55ºC. Shear bond strength values were measured using a universal testing machine. Student's t-test was used to compare the data (α=0.05. Failure mode was assessed using a stereomicroscope, and the treated and non-treated bracket surfaces were observed by scanning electron microscopy. RESULTS: Rebonded ceramic brackets treated with silica coating followed by silanization had significantly greater bond strength values (17.7±4.4 MPa than the sandblasting group (2.4±0.8 MPa, P<0.001. No significant difference was observed between the rebonded metal brackets treated with silica coating with silanization (15±3.9 MPa and the sandblasted brackets (13.6±3.9 MPa. Treated rebonded ceramic specimens primarily exhibited cohesive failure in resin and adhesive failure at the enamel-adhesive interface. CONCLUSIONS: In comparison to sandblasting, silica coating with aluminum trioxide particles followed by silanization resulted in higher bond strengths of rebonded ceramic brackets.

Shear Bond Strength of Orthodontic Brackets Bonded to Zirconium Crowns.

Science.gov (United States)

Mehmeti, Blerim; Azizi, Bleron; Kelmendi, Jeta; Iljazi-Shahiqi, Donika; Alar, Željko; Anić-Milošević, Sandra

2017-06-01

An increasing demand for esthetic restorations has resulted in an increased use of all-ceramic restorations, such as zirconium. However, one of the challenges the orthodontist must be willing to face is how to increase bond strength between the brackets and various ceramic restorations.Bond strength can beaffected bybracket type, by the material that bracketsaremade of, and their base surface design or retention mode. ​: A im: of this study was to perform a comparative analysis of the shear bond strength (SBS) of metallic and ceramic orthodontic brackets bonded to all-zirconium ceramic surfaces used for prosthetic restorations, and also to evaluate the fracture mode of these two types of orthodontic brackets. Twenty samples/semi-crowns of all-zirconium ceramic, on which orthodontic brackets were bonded, 10 metallic and 10 ceramic polycrystalline brackets, were prepared for this research. SBS has been testedby Universal Testing Machine, with a load applied using a knife edged rod moving at a fixed rate of 1 mm/min, until failure occurred. The force required to debond the brackets was recorded in Newton, then SBS was calculated to MPa. In addition, the samples were analyzed using a digital camera magnifier to determine Adhesive Remnant Index (ARI). Statistical data were processed using t-test, and the level of significance was set at α = 0.05. Higher shear bond strength values were observed in metallic brackets bonded to zirconium crowns compared tothoseof ceramic brackets, with a significant difference. During the test, two of the ceramic brackets were partially or totally damaged. Metallic brackets, compared to ceramic polycrystalline brackets, seemed tocreate stronger adhesion with all-zirconium surfaces due to their better retention mode. Also, ceramic brackets showed higher fragility during debonding.

Alkane Activation at Ambient Temperatures: Unusual Selectivities, C-C, C-H Bond Scission versus C-C Bond Coupling

NARCIS (Netherlands)

Trionfetti, C.; Agiral, A.; Gardeniers, Johannes G.E.; Lefferts, Leonardus; Seshan, Kulathuiyer

2008-01-01

Activating bonds: A cold plasma generated by dielectric barrier discharge in a microreactor converts alkanes (C1–C3) at atmospheric pressure. Large amounts of products with higher molecular weight than the starting hydrocarbons are observed showing that C-H activation at lower T favourably leads to

The active site of hen egg-white lysozyme: flexibility and chemical bonding

Energy Technology Data Exchange (ETDEWEB)

Held, Jeanette, E-mail: jeanette.netzel@uni-bayreuth.de; Smaalen, Sander van [University of Bayreuth, D-95440 Bayreuth (Germany)

2014-04-01

Chemical bonding at the active site of lysozyme is analyzed on the basis of a multipole model employing transferable multipole parameters from a database. Large B factors at low temperatures reflect frozen-in disorder, but therefore prevent a meaningful free refinement of multipole parameters. Chemical bonding at the active site of hen egg-white lysozyme (HEWL) is analyzed on the basis of Bader’s quantum theory of atoms in molecules [QTAIM; Bader (1994 ▶), Atoms in Molecules: A Quantum Theory. Oxford University Press] applied to electron-density maps derived from a multipole model. The observation is made that the atomic displacement parameters (ADPs) of HEWL at a temperature of 100 K are larger than ADPs in crystals of small biological molecules at 298 K. This feature shows that the ADPs in the cold crystals of HEWL reflect frozen-in disorder rather than thermal vibrations of the atoms. Directly generalizing the results of multipole studies on small-molecule crystals, the important consequence for electron-density analysis of protein crystals is that multipole parameters cannot be independently varied in a meaningful way in structure refinements. Instead, a multipole model for HEWL has been developed by refinement of atomic coordinates and ADPs against the X-ray diffraction data of Wang and coworkers [Wang et al. (2007), Acta Cryst. D63, 1254–1268], while multipole parameters were fixed to the values for transferable multipole parameters from the ELMAM2 database [Domagala et al. (2012), Acta Cryst. A68, 337–351] . Static and dynamic electron densities based on this multipole model are presented. Analysis of their topological properties according to the QTAIM shows that the covalent bonds possess similar properties to the covalent bonds of small molecules. Hydrogen bonds of intermediate strength are identified for the Glu35 and Asp52 residues, which are considered to be essential parts of the active site of HEWL. Furthermore, a series of weak C�

The active site of hen egg-white lysozyme: flexibility and chemical bonding

International Nuclear Information System (INIS)

Held, Jeanette; Smaalen, Sander van

2014-01-01

Chemical bonding at the active site of lysozyme is analyzed on the basis of a multipole model employing transferable multipole parameters from a database. Large B factors at low temperatures reflect frozen-in disorder, but therefore prevent a meaningful free refinement of multipole parameters. Chemical bonding at the active site of hen egg-white lysozyme (HEWL) is analyzed on the basis of Bader’s quantum theory of atoms in molecules [QTAIM; Bader (1994 ▶), Atoms in Molecules: A Quantum Theory. Oxford University Press] applied to electron-density maps derived from a multipole model. The observation is made that the atomic displacement parameters (ADPs) of HEWL at a temperature of 100 K are larger than ADPs in crystals of small biological molecules at 298 K. This feature shows that the ADPs in the cold crystals of HEWL reflect frozen-in disorder rather than thermal vibrations of the atoms. Directly generalizing the results of multipole studies on small-molecule crystals, the important consequence for electron-density analysis of protein crystals is that multipole parameters cannot be independently varied in a meaningful way in structure refinements. Instead, a multipole model for HEWL has been developed by refinement of atomic coordinates and ADPs against the X-ray diffraction data of Wang and coworkers [Wang et al. (2007), Acta Cryst. D63, 1254–1268], while multipole parameters were fixed to the values for transferable multipole parameters from the ELMAM2 database [Domagala et al. (2012), Acta Cryst. A68, 337–351] . Static and dynamic electron densities based on this multipole model are presented. Analysis of their topological properties according to the QTAIM shows that the covalent bonds possess similar properties to the covalent bonds of small molecules. Hydrogen bonds of intermediate strength are identified for the Glu35 and Asp52 residues, which are considered to be essential parts of the active site of HEWL. Furthermore, a series of weak C�

New Results on Plasma Activated Bonding of Imprinted Polymer Features for Bio MEMS Applications

International Nuclear Information System (INIS)

Kettner, P; Pelzer, R L; Glinsner, T; Farrens, S; Lee, D

2006-01-01

Nanoimprint Lithography is a well-acknowledged low cost, high resolution, large area 3D patterning process for polymers. It includes the most promising methods: high pressure hot embossing (HE) and UV-Nanoimprint Lithography (UV-NIL). Curing of the imprinted structures is either done by cooling down below the glass transition temperature of the thermoplastic polymer in case of HE or by subsequent UV-light exposure and cross-linking in case of UV-NIL. Both techniques allow rapid prototyping for high volume production of fully patterned substrates for a wide range of materials. The advantages of using polymer substrates over common Micro-Electro-Mechanical Systems (MEMS) processing materials like glass, silicon or quartz are: bio-compatible surfaces, easy manufacturability, low cost for high volume production, suitable for use in micro- and nano-fabrication, low conductivity, wide range of optical properties just to name a few. We will present experimental results on HE processes with PMMA as well as UV-NIL imprints in selected UV-curable resists. In the second part of the work we will describe the bonding techniques for packaging of the micro or nano structures. Packaging of the imprinted features is a key technology for a wide variety of field of applications: μ-TAS, biochemistry, micro-mixers, micro-reactors, electrophoresis cells, life science, micro-optical and nano-optical applications (switches) nanofluidics, data storage, etc. for features down to sub-100 nm range. Most bonding techniques for polymer use adhesives as intermediate layers. We will demonstrate a promising technique for dense and very strong bonds using plasma activation of polymers and glass. This bonding technology allows for bonding at low temperatures well below the glass transition temperature of the polymers, which will ensure that the structures are not deformed

Density functional theory based-study of 5-fluorouracil adsorption on β-cristobalite (1 1 1) hydroxylated surface: The importance of H-bonding interactions

Energy Technology Data Exchange (ETDEWEB)

Simonetti, S., E-mail: ssimonet@uns.edu.ar [Universidad Nacional del Sur (UNS)—Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Bahía Blanca (Argentina); Universidad Tecnológica Nacional (UTN), Bahía Blanca (Argentina); Compañy, A. Díaz [Comisión de Investigaciones Científicas (CIC), Buenos Aires (Argentina); Pronsato, E.; Juan, A.; Brizuela, G. [Universidad Nacional del Sur (UNS)—Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Bahía Blanca (Argentina); Lam, A. [Instituto de Ciencia y Tecnología de Materiales (IMRE), Universidad de La Habana (Cuba)

2015-12-30

Graphical abstract: - Highlights: • Favorable energies results in optimum four adsorption geometries. • Silanols are partially weakening and establish H-bonds with polar groups of 5-FU drug. • Dispersion forces approach the 5-FU molecule toward the surface. • Electron exchange is presented after adsorption. • H-bonds stabilize the molecule playing significant role in the adsorption mechanism. - Abstract: Silica-based mesoporous materials have been recently proposed as an efficient support for the controlled release of a popular anticancer drug, 5-fluorouracil (5-FU). Although the relevance of this topic, the atomistic details about the specific surface-drug interactions and the energy of adsorption are almost unknown. In this work, theoretical calculations using the Vienna Ab-initio Simulation Package (VASP) applying Grimme's—D2 correction were performed to elucidate the drug–silica interactions and the host properties that control 5-FU drug adsorption on β-cristobalite (1 1 1) hydroxylated surface. This study shows that hydrogen bonding, electron exchange, and dispersion forces are mainly involved to perform the 5-FU adsorption onto silica. This phenomenon, revealed by favorable energies, results in optimum four adsorption geometries that can be adopted for 5-FU on the hydroxylated silica surface. Silanols are weakening in response to the molecule approach and establish H-bonds with polar groups of 5-FU drug. The final geometry of 5-FU adopted on hydroxylated silica surface is the results of H-bonding interactions which stabilize and fix the molecule to the surface and dispersion forces which approach it toward silica (1 1 1) plane. The level of hydroxylation of the SiO{sub 2} (1 1 1) surface is reflected by the elevated number of hydrogen bonds that play a significant role in the adsorption mechanisms.

Interstellar hydrogen bonding

Science.gov (United States)

Etim, Emmanuel E.; Gorai, Prasanta; Das, Ankan; Chakrabarti, Sandip K.; Arunan, Elangannan

2018-06-01

This paper reports the first extensive study of the existence and effects of interstellar hydrogen bonding. The reactions that occur on the surface of the interstellar dust grains are the dominant processes by which interstellar molecules are formed. Water molecules constitute about 70% of the interstellar ice. These water molecules serve as the platform for hydrogen bonding. High level quantum chemical simulations for the hydrogen bond interaction between 20 interstellar molecules (known and possible) and water are carried out using different ab-intio methods. It is evident that if the formation of these species is mainly governed by the ice phase reactions, there is a direct correlation between the binding energies of these complexes and the gas phase abundances of these interstellar molecules. Interstellar hydrogen bonding may cause lower gas abundance of the complex organic molecules (COMs) at the low temperature. From these results, ketenes whose less stable isomers that are more strongly bonded to the surface of the interstellar dust grains have been observed are proposed as suitable candidates for astronomical observations.

Actor Bonds in Situations of Discontinuous Business Activities

DEFF Research Database (Denmark)

Skaates, Maria Anne

2000-01-01

Demand in many industrial buying situations, e.g. project purchases or procurement related to virtual organizations, is discontinuous. In situations of discontinuity, networks are often more of an ad hos informational and social nature, as strong activity and resource links are not present....... Furthermore the governance structure of markets characterized by discontinuous business activities is either that of the "socially constructed market" (Skaates, 2000) or that of the (socially constructed) network (Håkansson and Johanson, 1993). Additionally relationships and actor bonds vary substantially...

SEM/XPS analysis of fractured adhesively bonded graphite fibre surface resin-rich/graphite fibre composites

Science.gov (United States)

Devilbiss, T. A.; Wightman, J. P.; Progar, D. J.

1988-01-01

Samples of graphite fiber-reinforced polyimide were fabricated allowing the resin to accumulate at the composite surface. These surface resin-rich composites were then bonded together and tested for lap shear strength both before and after thermal aging. Lap shear strength did not appear to show a significant improvement over that previously recorded for resin-poor samples and was shown to decrease with increasing aging time and temperature.

Effect of surface treatment of prefabricated teeth on shear bond strength of orthodontic brackets

OpenAIRE

Cumerlato, Marina; Lima, Eduardo Martinelli de; Osorio, Leandro Berni; Mota, Eduardo Gonçalves; Menezes, Luciane Macedo de; Rizzatto, Susana Maria Deon

2017-01-01

ABSTRACT Objective: The aim of this in vitro study was to evaluate and compare the effects of grinding, drilling, sandblasting, and ageing prefabricated teeth (PfT) on the shear bond strength (SBS) of orthodontic brackets, as well as the effects of surface treatments on the adhesive remnant index (ARI). Methods: One-hundred-ninety-two PfT were divided into four groups (n = 48): Group 1, no surface treatment was done; Group 2, grinding was performed with a cylindrical diamond bur; Group 3,...

29-Silicon NMR evidence for the improved chromatographic siloxane bond stability of bulky alkylsilane ligands on a silica surface

NARCIS (Netherlands)

Scholten, A.B.; Haan, de J.W.; Claessens, H.A.; Ven, van de L.J.M.; Cramers, C.A.

1994-01-01

A stable bond stationary phase for reversed-phase HPLC, with a diisobutyl-n-octadecylsilane derivatized surface, was studied using 29Si CPMAS NMR. Fumed silica surfaces (Aerosil), trimethylsilylated to different extents, were used to illustrate the effect of ligand surface loading on the hydrogen

A study on poly (N-vinyl-2-pyrrolidone covalently bonded NiTi surface for inhibiting protein adsorption

Directory of Open Access Journals (Sweden)

Hongyan Yu

2016-12-01

Full Text Available Near equiatomic NiTi alloys have been extensively applied as biomaterials owing to its unique shape memory effect, superelasticity and biocompatibility. It has been demonstrated that surfaces capable of preventing plasma protein adsorption could reduce the reactivity of biomaterials with human blood. This motivated a lot of researches on the surface modification of NiTi alloy. In the present work, following heat and alkaline treatment and silanization by trichlorovinylsilane (TCVS, coating of poly (N-vinyl-2-pyrrolidone (PVP was produced on the NiTi alloy by gamma ray induced chemical bonding. The structures and properties of modified NiTi were characterized and in vitro biocompatibility of plasma protein adsorption was investigated. The results indicated that heat treatment at 823 K for 1 h could result in the formation of a protective TiO2 layer with “Ni-free” zone on NiTi surface. It was found that PVP was covalently bonded on NiTi surface to create a hydrophilic layer for inhibiting protein adsorption on the surface. The present work offers a green approach to introduce a bioorganic surface on metal and other polymeric or inorganic substrates by gamma irradiation.

The effects of various surface treatments on the shear bond strengths of stainless steel brackets to artificially-aged composite restorations.

Science.gov (United States)

Eslamian, Ladan; Borzabadi-Farahani, Ali; Mousavi, Nasim; Ghasemi, Amir

2011-05-01

To compare the shear bond strengths (SBS) of stainless steel brackets bonded to artificially-aged composite restorations after different surface treatments. Forty-five premolar teeth were restored with a nano-hybrid composite (Tetric EvoCeram), stored in deionised water for one week and randomly divided into three equal groups: Group I, he restorations were exposed to 5 per cent hydrofluoric acid for 60 seconds; Group II, the restorations were abraded with a micro-etcher (50 Iim alumina particles); Group III, the restorations were roughened with a coarse diamond bur. Similar premolar brackets were bonded to each restoration using the same resin adhesive and the specimens were then cycled in deionised water between 5 degrees C and 55 degrees C (500 cycles). The shear bond strengths were determined with a universal testing machine at a crosshead speed of 1 mm/min. The teeth and brackets were examined under a stereomicroscope and the adhesive remnants on the teeth scored with the adhesive remnant index (ARI). Specimens treated with the diamond bur had a significantly higher SBS (Mean: 18.45 +/- 3.82 MPa) than the group treated with hydrofluoric acid (Mean: 12.85 +/- 5.20 MPa). The mean SBS difference between the air-abrasion (Mean: 15.36 +/- 4.92 MPa) and hydrofluoric acid groups was not significant. High ARI scores occurred following abrasion with a diamond bur (100 per cent) and micro-etcher (80 per cent). In approximately two thirds of the teeth no adhesive was left on the restoration after surface treatment with hydofluoric acid. Surface treatment with a diamond bur resulted in a high bond strength between stainless steel brackets and artificially-aged composite restorations and was considered to be a safe and effective method of surface treatment. Most of the adhesive remained on the tooth following surface treatment with either the micro-etcher or the diamond bur.

A comparison of shear bond strength of orthodontic brackets bonded with four different orthodontic adhesives

Science.gov (United States)

Sharma, Sudhir; Tandon, Pradeep; Nagar, Amit; Singh, Gyan P; Singh, Alka; Chugh, Vinay K

2014-01-01

Objectives: The objective of this study is to compare the shear bond strength (SBS) of stainless steel (SS) orthodontic brackets bonded with four different orthodontic adhesives. Materials and Methods: Eighty newly extracted premolars were bonded to 0.022 SS brackets (Ormco, Scafati, Italy) and equally divided into four groups based on adhesive used: (1) Rely-a-Bond (self-cure adhesive, Reliance Orthodontic Product, Inc., Illinois, USA), (2) Transbond XT (light-cure adhesive, 3M Unitek, CA, USA), (3) Transbond Plus (sixth generation self-etch primer, 3M Unitek, CA, USA) with Transbond XT (4) Xeno V (seventh generation self-etch primer, Dentsply, Konstanz, Germany) with Xeno Ortho (light-cure adhesive, Dentsply, Konstanz, Germany) adhesive. Brackets were debonded with a universal testing machine (Model No. 3382 Instron Corp., Canton, Mass, USA). The adhesive remnant index (ARI) was recordedIn addition, the conditioned enamel surfaces were observed under a scanning electron microscope (SEM). Results: Transbond XT (15.49 MPa) attained the highest bond strength. Self-etching adhesives (Xeno V, 13.51 MPa; Transbond Plus, 11.57 MPa) showed clinically acceptable SBS values and almost clean enamel surface after debonding. The analysis of variance (F = 11.85, P adhesives left on the tooth) to be the most prevalent in Transbond XT (40%), followed by Rely-a-Bond (30%), Transbond Plus with Transbond XT (15%), and Xeno V with Xeno Ortho (10%). Under SEM, enamel surfaces after debonding of the brackets appeared porous when an acid-etching process was performed on the surfaces of Rely-a-Bond and Transbond XT, whereas with self-etching primers enamel presented smooth and almost clean surfaces (Transbond Plus and Xeno V group). Conclusion: All adhesives yielded SBS values higher than the recommended bond strength (5.9-7–8 MPa), Seventh generation self-etching primer Xeno V with Xeno Ortho showed clinically acceptable SBS and the least amount of residual adhesive left on the

Activation of C-H bond in methane by Pd atom from the bonding evolution theory perspective.

Science.gov (United States)

Nizovtsev, Anton S

2013-08-15

We report detailed study focused on the electron density redistribution during the simple oxidative addition reaction being the crucial stage of various catalytic processes. The bonding evolution theory based on the electron localization function and Thom's catastrophe theory shows that activation of methane's C-H bond by Pd atom consist of six elementary steps. The important feature revealed is the pronounced reorganization of Pd's outer core maxima corresponding to N-shell electrons of metal. Electronic rearrangements identified in this model reaction are likely to be the case in the more complex reactions of the same type involving transition metal compounds and, in principle, can be observed by modern ultrafast spectroscopy and diffraction techniques. Copyright © 2013 Wiley Periodicals, Inc.

Grafting of diazonium salts on oxides surface: formation of aryl-O bonds on iron oxide nanoparticles

Science.gov (United States)

Brymora, Katarzyna; Fouineau, Jonathan; Eddarir, Asma; Chau, François; Yaacoub, Nader; Grenèche, Jean-Marc; Pinson, Jean; Ammar, Souad; Calvayrac, Florent

2015-11-01

Combining ab initio modeling and 57Fe Mössbauer spectrometry, we characterized the nature of the chemical linkage of aminoalkyl arenediazonium salt on the surface of iron oxide nanoparticles. We established that it is built through a metal-oxygen-carbon bonding and not a metal-carbon one, as usually suggested and commonly observed in previously studied metal- or carbon-based surfaces.

Grafting of diazonium salts on oxides surface: formation of aryl-O bonds on iron oxide nanoparticles

International Nuclear Information System (INIS)

Brymora, Katarzyna; Fouineau, Jonathan; Eddarir, Asma; Chau, François; Yaacoub, Nader; Grenèche, Jean-Marc; Pinson, Jean; Ammar, Souad; Calvayrac, Florent

2015-01-01

Combining ab initio modeling and 57 Fe Mössbauer spectrometry, we characterized the nature of the chemical linkage of aminoalkyl arenediazonium salt on the surface of iron oxide nanoparticles. We established that it is built through a metal–oxygen–carbon bonding and not a metal–carbon one, as usually suggested and commonly observed in previously studied metal- or carbon-based surfaces

Grafting of diazonium salts on oxides surface: formation of aryl-O bonds on iron oxide nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Brymora, Katarzyna [LUNAM Université du Maine, IMMM UMR CNRS 6283 (France); Fouineau, Jonathan; Eddarir, Asma; Chau, François [Université Paris Diderot, Sorbonne Paris Cité, ITODYS CNRS UMR 7086 (France); Yaacoub, Nader; Grenèche, Jean-Marc [LUNAM Université du Maine, IMMM UMR CNRS 6283 (France); Pinson, Jean; Ammar, Souad [Université Paris Diderot, Sorbonne Paris Cité, ITODYS CNRS UMR 7086 (France); Calvayrac, Florent, E-mail: florent.calvayrac@univ-lemans.fr [LUNAM Université du Maine, IMMM UMR CNRS 6283 (France)

2015-11-15

Combining ab initio modeling and {sup 57}Fe Mössbauer spectrometry, we characterized the nature of the chemical linkage of aminoalkyl arenediazonium salt on the surface of iron oxide nanoparticles. We established that it is built through a metal–oxygen–carbon bonding and not a metal–carbon one, as usually suggested and commonly observed in previously studied metal- or carbon-based surfaces.

Heterogeneous Amyloid β-Sheet Polymorphs Identified on Hydrogen Bond Promoting Surfaces Using 2D SFG Spectroscopy.

Science.gov (United States)

Ho, Jia-Jung; Ghosh, Ayanjeet; Zhang, Tianqi O; Zanni, Martin T

2018-02-08

Two-dimensional sum-frequency generation spectroscopy (2D SFG) is used to study the structures of the pentapeptide FGAIL on hydrogen bond promoting surfaces. FGAIL is the most amyloidogenic portion of the human islet amyloid polypeptide (hIAPP or amylin). In the presence of a pure gold surface, FGAIL does not form ordered structures. When the gold is coated with a self-assembled monolayer of mercaptobenzoic acid (MBA), 2D SFG spectra reveal features associated with β-sheets. Also observed are cross peaks between the FGAIL peptides and the carboxylic acid groups of the MBA monolayer, indicating that the peptides are in close contact with the surface headgroups. In the second set of samples, FGAIL peptides chemically ligated to the MBA monolayer also exhibited β-sheet features but with a much simpler spectrum. From simulations of the experiments, we conclude that the hydrogen bond promoting surface catalyzes the formation of both parallel and antiparallel β-sheet structures with several different orientations. When ligated, parallel sheets with only a single orientation are the primary structure. Thus, this hydrogen bond promoting surface creates a heterogeneous distribution of polymorph structures, consistent with a concentration effect that allows nucleation of many different amyloid seeding structures. A single well-defined seed favors one polymorph over the others, showing that the concentrating influence of a membrane can be counterbalanced by factors that favor directed fiber growth. These experiments lay the foundation for the measurement and interpretation of β-sheet structures with heterodyne-detected 2D SFG spectroscopy. The results of this model system suggest that a heterogeneous distribution of polymorphs found in nature are an indication of nonselective amyloid aggregation whereas a narrow distribution of polymorph structures is consistent with a specific protein or lipid interaction that directs fiber growth.

Development of a classical force field for the oxidized Si surface: application to hydrophilic wafer bonding.

Science.gov (United States)

Cole, Daniel J; Payne, Mike C; Csányi, Gábor; Spearing, S Mark; Colombi Ciacchi, Lucio

2007-11-28

We have developed a classical two- and three-body interaction potential to simulate the hydroxylated, natively oxidized Si surface in contact with water solutions, based on the combination and extension of the Stillinger-Weber potential and of a potential originally developed to simulate SiO(2) polymorphs. The potential parameters are chosen to reproduce the structure, charge distribution, tensile surface stress, and interactions with single water molecules of a natively oxidized Si surface model previously obtained by means of accurate density functional theory simulations. We have applied the potential to the case of hydrophilic silicon wafer bonding at room temperature, revealing maximum room temperature work of adhesion values for natively oxidized and amorphous silica surfaces of 97 and 90 mJm(2), respectively, at a water adsorption coverage of approximately 1 ML. The difference arises from the stronger interaction of the natively oxidized surface with liquid water, resulting in a higher heat of immersion (203 vs 166 mJm(2)), and may be explained in terms of the more pronounced water structuring close to the surface in alternating layers of larger and smaller densities with respect to the liquid bulk. The computed force-displacement bonding curves may be a useful input for cohesive zone models where both the topographic details of the surfaces and the dependence of the attractive force on the initial surface separation and wetting can be taken into account.

Copper wire bonding

CERN Document Server

Chauhan, Preeti S; Zhong, ZhaoWei; Pecht, Michael G

2014-01-01

This critical volume provides an in-depth presentation of copper wire bonding technologies, processes and equipment, along with the economic benefits and risks.  Due to the increasing cost of materials used to make electronic components, the electronics industry has been rapidly moving from high cost gold to significantly lower cost copper as a wire bonding material.  However, copper wire bonding has several process and reliability concerns due to its material properties.  Copper Wire Bonding book lays out the challenges involved in replacing gold with copper as a wire bond material, and includes the bonding process changes—bond force, electric flame off, current and ultrasonic energy optimization, and bonding tools and equipment changes for first and second bond formation.  In addition, the bond–pad metallurgies and the use of bare and palladium-coated copper wires on aluminum are presented, and gold, nickel and palladium surface finishes are discussed.  The book also discusses best practices and re...

Interface bonding of NiCrAlY coating on laser modified H13 tool steel surface

Science.gov (United States)

Reza, M. S.; Aqida, S. N.; Ismail, I.

2016-06-01

Bonding strength of thermal spray coatings depends on the interfacial adhesion between bond coat and substrate material. In this paper, NiCrAlY (Ni-164/211 Ni22 %Cr10 %Al1.0 %Y) coatings were developed on laser modified H13 tool steel surface using atmospheric plasma spray (APS). Different laser peak power, P p, and duty cycle, DC, were investigated in order to improve the mechanical properties of H13 tool steel surface. The APS spraying parameters setting for coatings were set constant. The coating microstructure near the interface was analyzed using IM7000 inverted optical microscope. Interface bonding of NiCrAlY was investigated by interfacial indentation test (IIT) method using MMT-X7 Matsuzawa Hardness Tester Machine with Vickers indenter. Diffusion of atoms along NiCrAlY coating, laser modified and substrate layers was investigated by energy-dispersive X-ray spectroscopy (EDXS) using Hitachi Tabletop Microscope TM3030 Plus. Based on IIT method results, average interfacial toughness, K avg, for reference sample was 2.15 MPa m1/2 compared to sample L1 range of K avg from 6.02 to 6.96 MPa m1/2 and sample L2 range of K avg from 2.47 to 3.46 MPa m1/2. Hence, according to K avg, sample L1 has the highest interface bonding and is being laser modified at lower laser peak power, P p, and higher duty cycle, DC, prior to coating. The EDXS analysis indicated the presence of Fe in the NiCrAlY coating layer and increased Ni and Cr composition in the laser modified layer. Atomic diffusion occurred in both coating and laser modified layers involved in Fe, Ni and Cr elements. These findings introduce enhancement of coating system by substrate surface modification to allow atomic diffusion.

Controlling the bond scission sequence of oxygenates for energy applications

Science.gov (United States)

Stottlemyer, Alan L.

The so called "Holy Grail" of heterogeneous catalysis is a fundamental understanding of catalyzed chemical transformations which span multidimensional scales of both length and time, enabling rational catalyst design. Such an undertaking is realizable only with an atomic level understanding of bond formation and destruction with respect to intrinsic properties of the metal catalyst. In this study, we investigate the bond scission sequence of small oxygenates (methanol, ethanol, ethylene glycol) on bimetallic transition metal catalysts and transition metal carbide catalysts. Oxygenates are of interest both as hydrogen carriers for reforming to H2 and CO and as fuels in direct alcohol fuel cells (DAFC). To address the so-called "materials gap" and "pressure gap" this work adopted three parallel research approaches: (1) ultra high vacuum (UHV) studies including temperature programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS) on polycrystalline surfaces; (2) DFT studies including thermodynamic and kinetic calculations; (3) electrochemical studies including cyclic voltammetry (CV) and chronoamperometry (CA). Recent studies have suggested that tungsten monocarbide (WC) may behave similarly to Pt for the electrooxidation of oxygenates. TPD was used to quantify the activity and selectivity of oxygenate decomposition for WC and Pt-modifiedWC (Pt/WC) as compared to Pt. While decomposition activity was generally higher on WC than on Pt, scission of the C-O bond resulted in alkane/alkene formation on WC, an undesired product for DAFC. When Pt was added to WC by physical vapor deposition C-O bond scission was limited, suggesting that Pt synergistically modifies WC to improve the selectivity toward C-H bond scission to produce H2 and CO. Additionally, TPD confirmed WC and Pt/WC to be more CO tolerant than Pt. HREELS results verified that surface intermediates were different on Pt/WC as compared to Pt or WC and evidence of aldehyde

Patched bimetallic surfaces are active catalysts for ammonia decomposition.

Science.gov (United States)

Guo, Wei; Vlachos, Dionisios G

2015-10-07

Ammonia decomposition is often used as an archetypical reaction for predicting new catalytic materials and understanding the very reason of why some reactions are sensitive on material's structure. Core-shell or surface-segregated bimetallic nanoparticles expose outstanding activity for many heterogeneously catalysed reactions but the reasons remain elusive owing to the difficulties in experimentally characterizing active sites. Here by performing multiscale simulations in ammonia decomposition on various nickel loadings on platinum (111), we show that the very high activity of core-shell structures requires patches of the guest metal to create and sustain dual active sites: nickel terraces catalyse N-H bond breaking and nickel edge sites drive atomic nitrogen association. The structure sensitivity on these active catalysts depends profoundly on reaction conditions due to kinetically competing relevant elementary reaction steps. We expose a remarkable difference in active sites between transient and steady-state studies and provide insights into optimal material design.

Low temperature anodic bonding to silicon nitride

DEFF Research Database (Denmark)

Weichel, Steen; Reus, Roger De; Bouaidat, Salim

2000-01-01

Low-temperature anodic bonding to stoichiometric silicon nitride surfaces has been performed in the temperature range from 3508C to 4008C. It is shown that the bonding is improved considerably if the nitride surfaces are either oxidized or exposed to an oxygen plasma prior to the bonding. Both bu...

Effect of water storage and surface treatments on the tensile bond strength of IPS Empress 2 ceramic.

Science.gov (United States)

Salvio, Luciana A; Correr-Sobrinho, Lourenço; Consani, Simonides; Sinhoreti, Mário A C; de Goes, Mario F; Knowles, Jonathan C

2007-01-01

The aim of this study was to evaluate the effect of water storage (24 hours and 1 year) on the tensile bond strength between the IPS Empress 2 ceramic and Variolink II resin cement under different superficial treatments. One hundred and eighty disks with diameters of 5.3 mm at the top and 7.0 mm at the bottom, and a thickness of 2.5 mm were made, embedded in resin, and randomly divided into six groups: Groups 1 and 4 = 10% hydrofluoric acid for 20 seconds; Groups 2 and 5 = sandblasting for 5 seconds with 50 microm aluminum oxide; and Groups 3 and 6 = sandblasting for 5 seconds with 100 microm aluminum oxide. Silane was applied on the treated ceramic surfaces, and the disks were bonded into pairs with adhesive resin cement. The samples of Groups 1 to 3 were stored in distilled water at 37 degrees C for 24 hours, and Groups 4 to 6 were stored for 1 year. The samples were subjected to a tensile strength test in an Instron universal testing machine at a crosshead speed of 1.0 mm/min, until failure. The data were submitted to analysis of variance and Tukey's test (5%). The means of the tensile bond strength of Groups 1, 2, and 3 (15.54 +/- 4.53, 10.60 +/- 3.32, and 7.87 +/- 2.26 MPa) for 24-hour storage time were significantly higher than those observed for the 1-year storage (Groups 4, 5, and 6: 10.10 +/- 3.17, 6.34 +/- 1.06, and 2.60 +/- 0.41 MPa). The surface treatments with 10% hydrofluoric acid (15.54 +/- 4.53 and 10.10 +/- 3.17 MPa) showed statistically higher tensile bond strengths compared with sandblasting with 50 microm(10.60 +/- 3.32 and 6.34 +/- 1.06 MPa) and 100 microm (7.87 +/- 2.26 and 2.60 +/- 0.41 MPa) aluminum oxide for the storage time 24 hours and 1 year. Storage time significantly decreased the tensile bond strength for both ceramic surface treatments. The application of 10% hydrofluoric acid resulted in stronger tensile bond strength values than those achieved with aluminum oxide.

Low-temperature Au/a-Si wafer bonding

International Nuclear Information System (INIS)

Jing, Errong; Xiong, Bin; Wang, Yuelin

2011-01-01

The Si/SiO 2 /Ti/Au–Au/Ti/a-Si/SiO 2 /Si bonding structure, which can also be used for the bonding of non-silicon material, was investigated for the first time in this paper. The bond quality test showed that the bond yield, bond repeatability and average shear strength are higher for this bonding structure. The interfacial microstructure analysis indicated that the Au-induced crystallization of the amorphous silicon process leads to big Si grains extending across the bond interface and Au filling the other regions of the bond interface, which result into a strong and void-free bond interface. In addition, the Au-induced crystallization reaction leads to a change in the IR images of the bond interface. Therefore, the IR microscope can be used to evaluate and compare the different bond strengths qualitatively. Furthermore, in order to verify the superiority of the bonding structure, the Si/SiO 2 /Ti/Au–a-Si/SiO 2 /Si (i.e. no Ti/Au layer on the a-Si surface) and Si/SiO 2 /Ti/Au–Au/Ti/SiO 2 /Si bonding structures (i.e. Au thermocompression bonding) were also investigated. For the Si/SiO 2 /Ti/Au–a-Si/SiO 2 /Si bonding structure, the poor bond quality is due to the native oxide layer on the a-Si surface, and for the Si/SiO 2 /Ti/Au–Au/Ti/SiO 2 /Si bonding structure, the poor bond quality is caused by the wafer surface roughness which prevents intimate contact and limits the interdiffusion at the bond interface.

Heat treatment following surface silanization in rebonded tribochemical silica-coated ceramic brackets: shear bond strength analysis

Directory of Open Access Journals (Sweden)

Emilia Adriane Silva

2013-07-01

Full Text Available OBJECTIVE: This study aimed to evaluate the effects of heat treatment on the tribochemical silica coating and silane surface conditioning and the bond strength of rebonded alumina monocrystalline brackets. MATERIAL AND METHODS: Sixty alumina monocrystalline brackets were randomly divided according to adhesive base surface treatments (n=20: Gc, no treatment (control; Gt, tribochemical silica coating + silane application; Gh, as per Gt + post-heat treatment (air flux at 100ºC for 60 s. Brackets were bonded to the enamel premolars surface with a light-polymerized resin and stored in distilled water at 37ºC for 100 days. Additionally, half the specimens of each group were thermocycled (6,000 cycles between 5-55ºC (TC. The specimens were submitted to the shear bond strength (SBS test using a universal testing machine (1 mm/min. Failure mode was assessed using optical and scanning electron microscopy (SEM, together with the surface roughness (Ra of the resin cement in the bracket using interference microscopy (IM. 2-way ANOVA and the Tukey test were used to compare the data (p>0.05. RESULTS: The strategies used to treat the bracket surface had an effect on the SBS results (p=0.0, but thermocycling did not (p=0.6974. Considering the SBS results (MPa, Gh-TC and Gc showed the highest values (27.59±6.4 and 27.18±2.9 and Gt-TC showed the lowest (8.45±6.7. For the Ra parameter, ANOVA revealed that the aging method had an effect (p=0.0157 but the surface treatments did not (p=0.458. For the thermocycled and non-thermocycled groups, Ra (µm was 0.69±0.16 and 1.12±0.52, respectively. The most frequent failure mode exhibited was mixed failure involving the enamel-resin-bracket interfaces. CONCLUSION: Regardless of the aging method, Gh promoted similar SBS results to Gc, suggesting that rebonded ceramic brackets are a more effective strategy.

Approximate critical surface of the bond-mixed square-lattice Ising model

International Nuclear Information System (INIS)

Levy, S.V.F.; Tsallis, C.; Curado, E.M.F.

1979-09-01

The critical surface of the quenched bond-mixed square-lattice spin-1/2 first-neighbour-interaction ferromagnetic Ising model (with exchange interactions J 1 and J 2 ) has been investigated. Through renormalization group and heuristical procedures, a very accurate (error inferior to 3x10 -4 in the variables t sub(i) = th (J sub(i)/k sub(b)T)) approximate numerical proposal for all points of this surface is presented. This proposal simultaneously satisfies all the available exact results concerning the surface, namely P sub(c) = 1/2, t sub(c) = √2 - 1, both limiting slopes in these points, and t 2 = (1-t 1 )/(1+t 1 ) for p = 1/2. Furthemore an analytic approximation (namely (1 - p) 1n(1 + t 1 ) + p 1n(1 + t 2 ) =(1/2)1n 2) is also proposed. In what concerns the available exact results, it only fails in reproducing one of the two limiting slopes, where there is an error of 1% in the derivative: these facts result in an estimated error less than 10 -3 (in the t-variables) for any points in the surface. (Author) [pt

Development of Statistical Process Control Methodology for an Environmentally Compliant Surface Cleaning Process in a Bonding Laboratory

Science.gov (United States)

Hutchens, Dale E.; Doan, Patrick A.; Boothe, Richard E.

1997-01-01

Bonding labs at both MSFC and the northern Utah production plant prepare bond test specimens which simulate or witness the production of NASA's Reusable Solid Rocket Motor (RSRM). The current process for preparing the bonding surfaces employs 1,1,1-trichloroethane vapor degreasing, which simulates the current RSRM process. Government regulations (e.g., the 1990 Amendments to the Clean Air Act) have mandated a production phase-out of a number of ozone depleting compounds (ODC) including 1,1,1-trichloroethane. In order to comply with these regulations, the RSRM Program is qualifying a spray-in-air (SIA) precision cleaning process using Brulin 1990, an aqueous blend of surfactants. Accordingly, surface preparation prior to bonding process simulation test specimens must reflect the new production cleaning process. The Bonding Lab Statistical Process Control (SPC) program monitors the progress of the lab and its capabilities, as well as certifies the bonding technicians, by periodically preparing D6AC steel tensile adhesion panels with EA-91 3NA epoxy adhesive using a standardized process. SPC methods are then used to ensure the process is statistically in control, thus producing reliable data for bonding studies, and identify any problems which might develop. Since the specimen cleaning process is being changed, new SPC limits must be established. This report summarizes side-by-side testing of D6AC steel tensile adhesion witness panels and tapered double cantilevered beams (TDCBs) using both the current baseline vapor degreasing process and a lab-scale spray-in-air process. A Proceco 26 inches Typhoon dishwasher cleaned both tensile adhesion witness panels and TDCBs in a process which simulates the new production process. The tests were performed six times during 1995, subsequent statistical analysis of the data established new upper control limits (UCL) and lower control limits (LCL). The data also demonstrated that the new process was equivalent to the vapor

Bonding auto-polymerising acrylic resin to acrylic denture teeth.

LENUS (Irish Health Repository)

Nagle, Susan

2009-09-01

This study investigated the effect of surface treatments on the shear bond strength of an auto-polymerising acrylic resin cured to acrylic denture teeth. The surface treatments included a combination of grit-blasting and\\/or wetting the surface with monomer. Samples were prepared and then stored in water prior to shear testing. The results indicated that the application of monomer to the surface prior to bonding did not influence the bond strength. Grit blasting was found to significantly increase the bond strength.

New sol–gel refractory coatings on chemically-bonded sand cores for foundry applications to improve casting surface quality

DEFF Research Database (Denmark)

Nwaogu, Ugochukwu Chibuzoh; Poulsen, T.; Stage, R.K.

2011-01-01

Foundry refractory coatings protect bonded sand cores and moulds from producing defective castings during the casting process by providing a barrier between the core and the liquid metal. In this study, new sol–gel refractory coating on phenolic urethane cold box (PUCB) core was examined. The coa......Foundry refractory coatings protect bonded sand cores and moulds from producing defective castings during the casting process by providing a barrier between the core and the liquid metal. In this study, new sol–gel refractory coating on phenolic urethane cold box (PUCB) core was examined......–gel coated cores have better surface quality than those from uncoated cores and comparable surface quality with the commercial coatings. Therefore, the new sol–gel coating has a potential application in the foundry industry for improving the surface finish of castings thereby reducing the cost of fettling...

Ge-Au eutectic bonding of Ge (100) single crystals

International Nuclear Information System (INIS)

Knowlton, W.B.; Beeman, J.W.; Emes, J.H.; Loretto, D.; Itoh, K.M.; Haller, E.E.

1993-01-01

The author present preliminary results on the eutectic bonding between two (100) Ge single crystal surfaces using thin films of Au ranging from 900 angstrom/surface to 300 angstrom/surface and Pd (10% the thickness of Au). Following bonding, plan view optical microscopy (OM) of the cleaved interface of samples with Au thicknesses ≤ 500 angstrom/surface show a eutectic morphology more conducive to phonon transmission through the bond interface. High resolution transmission electron microscopy (HRTEM) cross sectional interface studies of a 300 angstrom/surface Au sample show epitaxial growth of Ge. In sections of the bond, lattice continuity of the Ge is apparent through the interface. TEM studies also reveal heteroepitaxial growth of Au with a Au-Ge lattice mismatch of less than 2%. Eutectic bonds with 200 angstrom/surface Au have been attained with characterization pending. An optical polishing technique for Ge has been optimized to insure intimate contact between the Ge surfaces prior to bonding. Interferometry analysis of the optically polished Ge surface shows that surface height fluctuations lie within ±150 angstrom across an interval of lmm. Characterization of phonon transmission through the interface is discussed with respect to low temperature detection of ballistic phonons

Lamb wave tuning curve calibration for surface-bonded piezoelectric transducers

International Nuclear Information System (INIS)

Sohn, Hoon; Lee, Sang Jun

2010-01-01

Surface-bonded lead zirconate titanate (PZT) transducers have been widely used for guided wave generation and measurement. For selective actuation and sensing of Lamb wave modes, the sizes of the transducers and the driving frequency of the input waveform should be tuned. For this purpose, a theoretical Lamb wave tuning curve (LWTC) of a specific transducer size is generally obtained. Here, the LWTC plots each Lamb wave mode' amplitude as a function of the driving frequency. However, a discrepancy between experimental and existing theoretical LWTCs has been observed due to little consideration of the bonding layer and the energy distribution between Lamb wave modes. In this study, calibration techniques for theoretical LWTCs are proposed. First, a theoretical LWTC is developed when circular PZT transducers are used for both Lamb wave excitation and sensing. Then, the LWTC is calibrated by estimating the effective PZT size with PZT admittance measurement. Finally, the energy distributions among symmetric and antisymmetric modes are taken into account for better prediction of the relative amplitudes between Lamb wave modes. The effectiveness of the proposed calibration techniques is examined through numerical simulations and experimental estimation of the LWTC using the circular PZT transducers instrumented on an aluminum plate

Bond strength of resin-resin interfaces contaminated with saliva and submitted to different surface treatments

DEFF Research Database (Denmark)

Furuse, Adilson Yoshio; da Cunha, Leonardo Fernandes; Benetti, Ana Raquel

2007-01-01

of silane and adhesive system. Resin cylinders were placed over the treated surfaces. The specimens were stored in water or ethanol. Shear bond strength tests were performed and the mode of failure was evaluated. Data were submitted to two-way ANOVA and Dunnett T3 test. Contamination of resin...

Critical surface of the quenched bond-diluted cubic model in self-dual lattice: renormalisation group approach

International Nuclear Information System (INIS)

Silva, E.P. da; Tsallis, C.

1991-01-01

We propose a quite simple real space renormalisation group which enables us to calculate (for the first time as far as we know, and presumably with high precision) the critical surface of the quenched bond-diluted discrete N-vector ferromagnet. (author)

Microstructure and surface properties of lignocellulosic-based activated carbons

International Nuclear Information System (INIS)

González-García, P.; Centeno, T.A.; Urones-Garrote, E.; Ávila-Brande, D.; Otero-Díaz, L.C.

2013-01-01

Highlights: ► Activated carbons were produced by KOH activation at 700 °C. ► The observed nanostructure consists of highly disordered graphene–like layers with sp 2 bond content ≈ 95%. ► Textural parameters show high surface area (≈ 1000 m 2 /g) and pore width of 1.3–1.8 nm. ► Specific capacitance reaches values as high as 161 F/g. - Abstract: Low cost activated carbons have been produced via chemical activation, by using KOH at 700 °C, from the bamboo species Guadua Angustifolia and Bambusa Vulgaris Striata and the residues from shells of the fruits of Castanea Sativa and Juglans Regia as carbon precursors. The scanning electron microscopy micrographs show the conservation of the precursor shape in the case of the Guadua Angustifolia and Bambusa Vulgaris Striata activated carbons. Transmission electron microscopy analyses reveal that these materials consist of carbon platelet–like particles with variable length and thickness, formed by highly disordered graphene–like layers with sp 2 content ≈ 95% and average mass density of 1.65 g/cm 3 (25% below standard graphite). Textural parameters indicate a high porosity development with surface areas ranging from 850 to 1100 m 2 /g and average pore width centered in the supermicropores range (1.3–1.8 nm). The electrochemical performance of the activated carbons shows specific capacitance values at low current density (1 mA/cm 2 ) as high as 161 F/g in the Juglans Regia activated carbon, as a result of its textural parameters and the presence of pseudocapacitance derived from surface oxygenated acidic groups (mainly quinones and ethers) identified in this activated carbon.

Effect of surface treatment of prefabricated teeth on shear bond strength of orthodontic brackets

Science.gov (United States)

Cumerlato, Marina; de Lima, Eduardo Martinelli; Osorio, Leandro Berni; Mota, Eduardo Gonçalves; de Menezes, Luciane Macedo; Rizzatto, Susana Maria Deon

2017-01-01

ABSTRACT Objective: The aim of this in vitro study was to evaluate and compare the effects of grinding, drilling, sandblasting, and ageing prefabricated teeth (PfT) on the shear bond strength (SBS) of orthodontic brackets, as well as the effects of surface treatments on the adhesive remnant index (ARI). Methods: One-hundred-ninety-two PfT were divided into four groups (n = 48): Group 1, no surface treatment was done; Group 2, grinding was performed with a cylindrical diamond bur; Group 3, two drillings were done with a spherical diamond bur; Group 4, sandblasting was performed with 50-µm aluminum oxide. Before the experiment, half of the samples stayed immersed in distilled water at 37oC for 90 days. Brackets were bonded with Transbond XT and shear strength tests were carried out using a universal testing machine. SBS were compared by surface treatment and by ageing with two-way ANOVA, followed by Tukey’s test. ARI scores were compared between surface treatments with Kruskal-Wallis test followed by Dunn’s test. Results: Surface treatments on PfT enhanced SBS of brackets (p< 0.01), result not observed with ageing (p= 0.45). Groups II, III, and IV showed higher SBS and greater ARI than the Group 1 (p< 0.05). SBS was greater in the groups 3 and 4 (drilling, sandblasting) than in the Group 2 (grinding) (p< 0.05). SBS and ARI showed a positive correlation (Spearman’s R2= 0.57; p< 0.05). Conclusion: Surface treatment on PfT enhanced SBS of brackets, however ageing did not show any relevance. Sandblasting and drilling showed greater SBS than grinding. There was a positive correlation between SBS and ARI. PMID:28902249

Effect of surface treatment of prefabricated teeth on shear bond strength of orthodontic brackets

Directory of Open Access Journals (Sweden)

Marina Cumerlato

Full Text Available ABSTRACT Objective: The aim of this in vitro study was to evaluate and compare the effects of grinding, drilling, sandblasting, and ageing prefabricated teeth (PfT on the shear bond strength (SBS of orthodontic brackets, as well as the effects of surface treatments on the adhesive remnant index (ARI. Methods: One-hundred-ninety-two PfT were divided into four groups (n = 48: Group 1, no surface treatment was done; Group 2, grinding was performed with a cylindrical diamond bur; Group 3, two drillings were done with a spherical diamond bur; Group 4, sandblasting was performed with 50-µm aluminum oxide. Before the experiment, half of the samples stayed immersed in distilled water at 37oC for 90 days. Brackets were bonded with Transbond XT and shear strength tests were carried out using a universal testing machine. SBS were compared by surface treatment and by ageing with two-way ANOVA, followed by Tukey’s test. ARI scores were compared between surface treatments with Kruskal-Wallis test followed by Dunn’s test. Results: Surface treatments on PfT enhanced SBS of brackets (p< 0.01, result not observed with ageing (p= 0.45. Groups II, III, and IV showed higher SBS and greater ARI than the Group 1 (p< 0.05. SBS was greater in the groups 3 and 4 (drilling, sandblasting than in the Group 2 (grinding (p< 0.05. SBS and ARI showed a positive correlation (Spearman’s R2= 0.57; p< 0.05. Conclusion: Surface treatment on PfT enhanced SBS of brackets, however ageing did not show any relevance. Sandblasting and drilling showed greater SBS than grinding. There was a positive correlation between SBS and ARI.

GROUT-CONCRETE INTERFACE BOND PERFORMANCE: EFFECT OF INTERFACE MOISTURE ON THE TENSILE BOND STRENGTH AND GROUT MICROSTRUCTURE.

Science.gov (United States)

De la Varga, I; Muñoz, J F; Bentz, D P; Spragg, R P; Stutzman, P E; Graybeal, B A

2018-05-01

Bond between two cementitious materials is crucial in applications such as repairs, overlays, and connections of prefabricated bridge elements (PBEs), to name just a few. It is the latter that has special interest to the authors of this paper. After performing a dimensional stability study on grout-like materials commonly used as connections between PBEs, it was observed that the so-called 'non-shrink' cementitious grouts showed a considerable amount of early-age shrinkage. This might have negative effects on the integrity of the structure, due not only to the grout material's early degradation, but also to a possible loss of bond between the grout and the prefabricated concrete element. Many factors affect the bond strength between two cementitious materials (e.g., grout-concrete), the presence of moisture at the existing concrete substrate surface being one of them. In this regard, pre-moistening the concrete substrate surface prior to the application of the grout material is sometimes recommended for bond enhancement. This topic has been the focus of numerous research studies in the past; however, there is still controversy among practitioners on the real benefits that this practice might provide. This paper evaluates the tensile bond performance of two non-shrink cementitious grouts applied to the exposed aggregate surface of a concrete substrate, and how the supply of moisture at the grout-concrete interface affects the bond strength. "Pull-off" bond results show increased tensile bond strength when the concrete surface is pre-moistened. Reasons to explain the observed increased bond strength are given after a careful microstructural analysis of the grout-concrete interface. Interfaces where sufficient moisture is provided to the concrete substrate such that moisture movement from the grout is prevented show reduced porosity and increased hydration on the grout side of the interface, which is thought to directly contribute to the increased tensile bond

BONDING ALUMINUM METALS

Science.gov (United States)

Noland, R.A.; Walker, D.E.

1961-06-13

A process is given for bonding aluminum to aluminum. Silicon powder is applied to at least one of the two surfaces of the two elements to be bonded, the two elements are assembled and rubbed against each other at room temperature whereby any oxide film is ruptured by the silicon crystals in the interface; thereafter heat and pressure are applied whereby an aluminum-silicon alloy is formed, squeezed out from the interface together with any oxide film, and the elements are bonded.

Hydrogen bond dynamical properties of adsorbed liquid water monolayers with various TiO2 interfaces

Science.gov (United States)

English, Niall J.; Kavathekar, Ritwik S.; MacElroy, J. M. D.

2012-12-01

Equilibrium classical molecular dynamics (MD) simulations have been performed to investigate the hydrogen-bonding kinetics of water in contact with rutile-(110), rutile-(101), rutile-(100), and anatase-(101) surfaces at room temperature (300 K). It was observed that anatase-(101) exhibits the longest-lived hydrogen bonds in terms of overall persistence, followed closely by rutile-(110). The relaxation times, defined as the integral of the autocorrelation of the hydrogen bond persistence function, were also longer for these two cases, while decay of the autocorrelation function was slower. The increased number and overall persistence of hydrogen bonds in the adsorbed water monolayers at these surfaces, particularly for anatase-(101), may serve to promote possible water photolysis activity thereon.

Preparation and photocatalytic activity of chemically-bonded phosphate ceramics containing TiO2

Science.gov (United States)

Martins, Monize Aparecida; de Lima, Bruna de Oliveira; Ferreira, Leticia Patrício; Colonetti, Emerson; Feltrin, Jucilene; De Noni, Agenor

2017-05-01

Titanium dioxide was incorporated into chemically-bonded phosphate ceramic for use as photocatalytic inorganic coating. The coatings obtained were applied to unglazed ceramic tiles and cured at 350 °C. The surfaces were characterized by photocatalytic activity, determined in aqueous medium, based on the degradation of methylene blue dye. The effects of the percentage of TiO2 and the thickness of the layer on the photocatalytic efficiency were evaluated. The influence of the incorporation of TiO2 on the consolidation of the phosphate matrix coating was investigated using the wear resistance test. The crystalline phases of the coatings obtained were determined by XRD. The microstructure of the surfaces was analyzed by SEM. The thermal curing treatment did not cause a phase transition from anatase to rutile. An increase in the photocatalytic activity of the coating was observed with an increase in the TiO2 content. The dye degradation indices ranged from 14.9 to 44.0%. The photocatalytic efficiency was not correlated with the thickness of the coating layer deposited. The resistance to wear decreased with an increase in the TiO2 content. Comparison with a commercial photocatalytic ceramic coating indicated that there is a range of values for the TiO2 contents which offer potential for photocatalytic applications.

Effect of ultraviolet light irradiation on bond strength of fiber post: Evaluation of surface characteristic and bonded area of fiber post with resin cement

OpenAIRE

Reza, Fazal; Ibrahim, Nur Sukainah

2015-01-01

Objective: Fiber post is cemented to a root canal to restore coronal tooth structure. This research aims to evaluate the effect of ultraviolet (UV) irradiation on bond strength of fiber post with resin cement. Materials and Methods: A total of 40 of the two types of fiber posts, namely, FRC Prostec (FRC) and Fiber KOR (KOR), were used for the experiment. UV irradiation was applied on top of the fiber post surface for 0, 15, 20, and 30 min. The irradiated surface of the fiber posts (n = 5) wer...

Assessment of Tensile Bond Strength of Fiber-Reinforced Composite Resin to Enamel Using Two Types of Resin Cements and Three Surface Treatment Methods

Directory of Open Access Journals (Sweden)

Tahereh Ghaffari

2015-10-01

Full Text Available Background: Resin-bonded bridgework with a metal framework is one of the most conservative ways to replace a tooth with intact abutments. Visibility of metal substructure and debonding are the complications of these bridgeworks. Today, with the introduction of fiber-reinforced composite resins, it is possible to overcome these complications. The aim of this study was to evaluate the bond strength of fiber-reinforced composite resin materials (FRC to enamel. Methods: Seventy-two labial cross-sections were prepared from intact extracted teeth. Seventy-two rectangular samples of cured Vectris were prepared and their thickness was increased by adding Targis. The samples were divided into 3 groups for three different surface treatments: sandblasting, etching with 9% hydrofluoric acid, and roughening with a round tapered diamond bur. Each group was then divided into two subgroups for bonding to etched enamel by Enforce and Variolink II resin cements. Instron universal testing machine was used to apply a tensile force. The fracture force was recorded and the mode of failure was identified under a reflective microscope. Results: There were no significant differences in bond strength between the three surface treatment groups (P=0.53. The mean bond strength of Variolink II cement was greater than that of Enforce (P=0.04. There was no relationship between the failure modes (cohesive and adhesive and the two cement types. There was some association between surface treatment and failure mode. There were adhesive failures in sandblasted and diamond-roughened groups and the cohesive failure was dominant in the etched group. Conclusion: It is recommended that restorations made of fiber-reinforced composite resin be cemented with VariolinkII and surface-treated by hydrofluoric acid.   Keywords: Tensile bond strength; surface treatment methods; fiber-reinforced composite resin

In vitro Assessment of Influence of Various Bleaching Protocols on the Strength of Ceramic Orthodontic Brackets bonded to Bleached Tooth Surface: A Comparative Study.

Science.gov (United States)

Iska, Divya; Devanna, Raghu; Singh, Madhvi; Chitumalla, Rajkiran; Balasubramanian, Sai C Bala; Goutam, Manish

2017-12-01

Esthetics is one of the common issues because of which patients consult dental orthodontic treatment. Two ways of tooth bleaching are available these days, which includes in-office bleach and home bleach. Various bleaching protocols are available these days for treating the tooth surfaces. Hence, we planned the present study for investigating the impact of various intracoronal bleaching protocols on shear bond strength of ceramic brackets bonded to tooth surface after bleaching. The present study included assessment of 100 extracted maxillary central incisors with the integrated buccal surface. A resin block was made and individual teeth were embedded in each block. Root canal therapy procedure was performed in all the teeth, after which 2 mm short of tooth apex up to the level of cementoenamel junction, removal of the root canal filling was done. All the samples were broadly divided into four study groups with 25 samples in each group. Bleaching procedure was carried in all the samples intracoronally followed by testing of shear bond strength using universal force testing machine. Following the modified adhesive remnant index (AI), assessment of remaining adhesive on the brackets was done. All the results were compiled and analyzed by Statistical Package for the Social Sciences (SPSS) software version 17.0. In the control group, mean shear bond strength was found to be 17.9 MPa. While comparing the carbamide peroxide (CP) group with sodium perborate study group, we observed a statistically significant difference. Nonsignificant results were obtained while comparing the shear bond strength in between sodium perborate group and hydrogen peroxide (HP) group. Intracoronal bleaching does affect the shear bond strength of ceramic brackets. Sodium perborate bleaching influences shear bond strength more strongly than other bleaching agents such as CP and HP. In patients undergoing orthodontic treatment, HP is a preferred agent where bleaching has to be followed by

Comparison of shear bond strength of amalgam bonded to primary and permanent dentin

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Mahdi S

2008-06-01

Full Text Available Amalgam′s non-adhesive characteristics necessitate cavity preparations incorporating retentive features, which often require the removal of non-carious tooth structure. Use of adhesives beneath amalgam restorations, would be helpful to overcome this disadvantage. This study was undertaken to compare the mean shear bond strength of amalgam bonded to primary and permanent dentin, to evaluate the efficacy of amalgam adhesives in pediatric dentistry.27 primary and 28 permanent posterior teeth with intact buccal or lingual surfaces were grounded to expose dentin and wet-polished with 400-grit silicone carbide paper. Scotchbond Multi Purpose Plus adhesive system was applied to the dentin surfaces and light cured. Amalgam was condensed onto the treated dentin through a plastic mold.shear bond strength testing was done using an Instron Universal testing machine, at a crosshead speed of 0.5 mm/min.The data were analyzed by independent samples t-test The difference among the two groups was not statistically significant (p>0.05 Bonded amalgam showed the same level of bond strength to primary and permanent dentin; so, application of amalgam bonding agents in pediatric dentistry can be recommended.

Degree of conversion and bond strength of resin-cements to feldspathic ceramic using different curing modes

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Veridiana Resende NOVAIS

Full Text Available Abstract Resin cements have led to great advances in dental ceramic restoration techniques because of their ability to bond to both dental structures and restorative materials. Objective The aim of this study was to assess the performance of resin cements when different curing modes are used, by evaluating the degree of conversion and bond strength to a ceramic substrate. Material and Methods Three resin cements were evaluated, two dual-cured (Variolink II and RelyX ARC and one light-cured (Variolink Veneer. The dual-cured resin cements were tested by using the dual activation mode (base and catalyst and light-activation mode (base paste only. For degree of conversion (DC (n=5, a 1.0 mm thick feldspathic ceramic disc was placed over the resin cement specimens and the set was light activated with a QTH unit. After 24 h storage, the DC was measured with Fourier transform infrared spectroscopy (FTIR. For microshear bond strength testing, five feldspathic ceramic discs were submitted to surface treatment, and three cylindrical resin cement specimens were bonded to each ceramic surface according to the experimental groups. After 24 h, microshear bond testing was performed at 0.5 mm/min crosshead speed until the failure. Data were submitted to one-way ANOVA followed by Tukey test (p<0.05. Scanning electron microscopy (SEM was used for classifying the failure modes. Results Higher DC and bond strength values were shown by the resin cements cured by using the dual activation mode. The Variolink II group presented higher DC and bond strength values when using light-activation only when compared with the Variolink Veneer group. Conclusion The base paste of dual-cured resin cements in light-activation mode can be used for bonding translucent ceramic restorations of up to or less than 1.0 mm thick.

Energy and Rate Determinations to Activate the C-C σ-BOND of Acetone by Gaseous NI^+

Science.gov (United States)

Castleberry, Vanessa A.; Dee, S. Jason; Villarroel, Otsmar J.; Laboren, Ivanna E.; Frey, Sarah E.; Bellert, Darrin J.

2009-06-01

A unique application of a custom fabricated photodissociation spectrometer permits the determination of thermodynamic properties (activation energies), reaction rates, and mechanistic details of bare metal cation mediated C-C σ-bond activation in the gas phase. Specifically, the products and rates resulting from the unimolecular decomposition of the Ni^+Acetone (Ni^+Ac) adduct are monitored after absorption of a known amount of energy. The three dissociative products which are observed in high yield are Ni^+, Ni^+CO, and CH3CO^+. The latter two fragment ions result from the activation of a C-C σ-bond. It was found that minimally 14 000 cm^{-1} of energy must be deposited into the adduct ion to induce C-C bond breakage. Preliminary results for the Ni^+ activation of the C-C σ-bond of acetone indicate that there are (at least) two low energy reaction coordinates leading to C-C bond breakage. The lower energy pathway emerges from the doublet ground state with an upper limit to the activation energy of 14 000 cm^{-1} and reaction rate ≈0.14 molecules/μs. The higher energy path is assumed to be along the quartet reaction coordinate with a minimum activation energy of 18 800 cm^{-1} (relative to the ground state) and a slightly slower reaction rate.

75 FR 68809 - Agency Information Collection Activities: Importation Bond Structure

Science.gov (United States)

2010-11-09

... DEPARTMENT OF HOMELAND SECURITY U.S. Customs And Border Protection Agency Information Collection Activities: Importation Bond Structure AGENCY: U.S. Customs and Border Protection, Department of Homeland... collection: 1651-0050. SUMMARY: U.S. Customs and Border Protection (CBP) of the Department of Homeland...

Direct Covalent Grafting of Phytate to Titanium Surfaces through Ti-O-P Bonding Shows Bone Stimulating Surface Properties and Decreased Bacterial Adhesion.

Science.gov (United States)

Córdoba, Alba; Hierro-Oliva, Margarita; Pacha-Olivenza, Miguel Ángel; Fernández-Calderón, María Coronada; Perelló, Joan; Isern, Bernat; González-Martín, María Luisa; Monjo, Marta; Ramis, Joana M

2016-05-11

Myo-inositol hexaphosphate, also called phytic acid or phytate (IP6), is a natural molecule abundant in vegetable seeds and legumes. Among other functions, IP6 inhibits bone resorption. It is adsorbed on the surface of hydroxyapatite, inhibiting its dissolution and decreasing the progressive loss of bone mass. We present here a method to directly functionalize Ti surfaces covalently with IP6, without using a cross-linker molecule, through the reaction of the phosphate groups of IP6 with the TiO2 layer of Ti substrates. The grafting reaction consisted of an immersion in an IP6 solution to allow the physisorption of the molecules onto the substrate, followed by a heating step to obtain its chemisorption, in an adaptation of the T-Bag method. The reaction was highly dependent on the IP6 solution pH, only achieving a covalent Ti-O-P bond at pH 0. We evaluated two acidic pretreatments of the Ti surface, to increase its hydroxylic content, HNO3 30% and HF 0.2%. The structure of the coated surfaces was characterized by X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, and ellipsometry. The stability of the IP6 coating after three months of storage and after sterilization with γ-irradiation was also determined. Then, we evaluated the biological effect of Ti-IP6 surfaces in vitro on MC3T3-E1 osteoblastic cells, showing an osteogenic effect. Finally, the effect of the surfaces on the adhesion and biofilm viability of oral microorganisms S. mutans and S. sanguinis was also studied, and we found that Ti-IP6 surfaces decreased the adhesion of S. sanguinis. A surface that actively improves osseointegration while decreasing the bacterial adhesion could be suitable for use in bone implants.

The effects of surface bond relaxation on electronic structure of Sb{sub 2}Te{sub 3} nano-films by first-principles calculation

Energy Technology Data Exchange (ETDEWEB)

Li, C., E-mail: canli1983@gmail.com; Zhao, Y. F.; Fu, C. X.; Gong, Y. Y. [Center for Coordination Bond Engineering, School of Materials Science and Engineering, China Jiliang University (China); Chi, B. Q. [College of Modem Science and Technology, Jiliang University, Hangzhou, 310018 (China); Sun, C. Q. [Center for Coordination Bond Engineering, School of Materials Science and Engineering, China Jiliang University (China); School of Electrical and Electronic Engineering, Nanyang Technological University, 639798 (Singapore)

2014-10-15

The effects of vertical compressive stress on Sb{sub 2}Te{sub 3} nano-films have been investigated by the first principles calculation, including stability, electronic structure, crystal structure, and bond order. It is found that the band gap of nano-film is sensitive to the stress in Sb{sub 2}Te{sub 3} nano-film and the critical thickness increases under compressive stress. The band gap and band order of Sb{sub 2}Te{sub 3} film has been affected collectively by the surface and internal crystal structures, the contraction ratio between surface bond length of nano-film and the corresponding bond length of bulk decides the band order of Sb{sub 2}Te{sub 3} film.

Influence of an oxygen-inhibited layer on enamel bonding of dental adhesive systems: surface free-energy perspectives.

Science.gov (United States)

Ueta, Hirofumi; Tsujimoto, Akimasa; Barkmeier, Wayne W; Oouchi, Hajime; Sai, Keiichi; Takamizawa, Toshiki; Latta, Mark A; Miyazaki, Masashi

2016-02-01

The influence of an oxygen-inhibited layer (OIL) on the shear bond strength (SBS) to enamel and surface free-energy (SFE) of adhesive systems was investigated. The adhesive systems tested were Scotchbond Multipurpose (SM), Clearfil SE Bond (CS), and Scotchbond Universal (SU). Resin composite was bonded to bovine enamel surfaces to determine the SBS, with and without an OIL, of adhesives. The SFE of cured adhesives with and without an OIL were determined by measuring the contact angles of three test liquids. There were no significant differences in the mean SBS of SM and CS specimens with or without an OIL; however, the mean SBS of SU specimens with an OIL was significantly higher than that of SU specimens without an OIL. For all three systems, the mean total SFE (γS), polarity force (γSp), and hydrogen bonding force (γSh) values of cured adhesives with an OIL were significantly higher than those of cured adhesives without an OIL. The results of this study indicate that the presence of an OIL promotes higher SBS of a single-step self-etch adhesive system, but not of a three-step or a two-step self-etch primer system. The SFE values of cured adhesives with an OIL were significantly higher than those without an OIL. The SFE characteristics of the OIL of adhesives differed depending on the type of adhesive. © 2015 Eur J Oral Sci.

Effect of Surface Treatment on Shear Bond Strength between Resin Cement and Ce-TZP/Al2O3

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Jong-Eun Kim

2016-01-01

Full Text Available Purpose. Although several studies evaluating the mechanical properties of Ce-TZP/Al2O3 have been published, to date, no study has been published investigating the bonding protocol between Ce-TZP/Al2O3 and resin cement. The aim of this study was to evaluate the shear bond strength to air-abraded Ce-TZP/Al2O3 when primers and two different cement types were used. Materials and Methods. Two types of zirconia (Y-TZP and Ce-TZP/Al2O3 specimens were further divided into four subgroups according to primer application and the cement used. Shear bond strength was measured after water storage for 3 days or 5,000 times thermocycling for artificial aging. Results. The Y-TZP block showed significantly higher shear bond strength than the Ce-TZP/Al2O3 block generally. Primer application promoted high bond strength and less effect on bond strength reduction after thermocycling, regardless of the type of cement, zirconia block, or aging time. Conclusions. Depending on the type of the primer or resin cement used after air-abrasion, different wettability of the zirconia surface can be observed. Application of primer affected the values of shear bond strength after the thermocycling procedure. In the case of using the same bonding protocol, Y-TZP could obtain significantly higher bond strength compared with Ce-TZP/Al2O3.

To evaluate and compare the effect of different Post Surface treatments on the Tensile Bond Strength between Fiber Posts and Composite Resin.

OpenAIRE

Shori, Deepa; Pandey, Swapnil; Kubde, Rajesh; Rathod, Yogesh; Atara, Rahul; Rathi, Shravan

2013-01-01

Background: Fiber posts are widely used for restoration of mutilated teeth that lack adequate coronal tooth structure to retain a core for definitive restoration, bond between the fiber post and composite material depends upon the chemical reaction between the post surface and the resin material used for building up the core. In attempt to maximize the resin bonding with fiber post, different post surface conditioning is advocated. Therefore the purpose of the study is to examine the interfac...

The road to the first, fully active and more stable human insulin variant with an additional disulfide bond

DEFF Research Database (Denmark)

Vinther, Tine N.; Kjeldsen, Thomas B.; Jensen, Knud Jørgen

2015-01-01

Insulin, a small peptide hormone, is crucial in maintaining blood glucose homeostasis. The stability and activity of the protein is directed by an intricate system involving disulfide bonds to stabilize the active monomeric species and by their non-covalent oligomerization. All known insulin...... variants in vertebrates consist of two peptide chains and have six cysteine residues, which form three disulfide bonds, two of them link the two chains and a third is an intra-chain bond in the A-chain. This classical insulin fold appears to have been conserved over half a billion years of evolution. We...... addressed the question whether a human insulin variant with four disulfide bonds could exist and be fully functional. In this review, we give an overview of the road to engineering four-disulfide bonded insulin analogs. During our journey, we discovered several active four disulfide bonded insulin analogs...

Initial Reduction of CO2 on Pd-, Ru-, and Cu-Doped CeO2(111) Surfaces: Effects of Surface Modification on Catalytic Activity and Selectivity.

Science.gov (United States)

Guo, Chen; Wei, Shuxian; Zhou, Sainan; Zhang, Tian; Wang, Zhaojie; Ng, Siu-Pang; Lu, Xiaoqing; Wu, Chi-Man Lawrence; Guo, Wenyue

2017-08-09

Surface modification by metal doping is an effective treatment technique for improving surface properties for CO 2 reduction. Herein, the effects of doped Pd, Ru, and Cu on the adsorption, activation, and reduction selectivity of CO 2 on CeO 2 (111) were investigated by periodic density functional theory. The doped metals distorted the configuration of a perfect CeO 2 (111) by weakening the adjacent Ce-O bond strength, and Pd doping was beneficial for generating a highly active O vacancy. The analyses of adsorption energy, charge density difference, and density of states confirmed that the doped metals were conducive for enhancing CO 2 adsorption, especially for Cu/CeO 2 (111). The initial reductive dissociation CO 2 → CO* + O* on metal-doped CeO 2 (111) followed the sequence of Cu- > perfect > Pd- > Ru-doped CeO 2 (111); the reductive hydrogenation CO 2 + H → COOH* followed the sequence of Cu- > perfect > Ru- > Pd-doped CeO 2 (111), in which the most competitive route on Cu/CeO 2 (111) was exothermic by 0.52 eV with an energy barrier of 0.16 eV; the reductive hydrogenation CO 2 + H → HCOO* followed the sequence of Ru- > perfect > Pd-doped CeO 2 (111). Energy barrier decomposition analyses were performed to identify the governing factors of bond activation and scission along the initial CO 2 reduction routes. Results of this study provided deep insights into the effect of surface modification on the initial reduction mechanisms of CO 2 on metal-doped CeO 2 (111) surfaces.

Shear bond strength of a new one-bottle dentin adhesive.

Science.gov (United States)

Swift, E J; Bayne, S C

1997-08-01

To test the shear bond strength of a new adhesive, 3M Single Bond, to dentin surfaces containing different degrees of moisture. Two commercially available one-bottle adhesives (Prime & Bond, One-Step) and a conventional three-step system (Scotchbond Multi-Purpose Plus) were included for comparison. 120 bovine teeth were embedded in acrylic and the labial surfaces were polished to 600 grit to create standardized dentin surfaces for testing. Resin composite was bonded to dentin using a gelatin capsule technique. Four adhesive systems were evaluated with three different degrees of surface moisture (moist, wet, and overwet). Shear bond strengths of adhesives to dentin were determined using a universal testing machine and analyzed by ANOVA and Tukey's post hoc tests. Single Bond had mean shear bond strengths of 19.2, 23.2 and 20.3 MPa to moist, wet, and overwet dentin, respectively. Bond strengths of the three-component system Scotchbond Multi-Purpose Plus ranged from 23.1 to 25.3 MPa, but were not significantly higher than the values for Single Bond. Prime & Bond had bond strengths similar to those of Single Bond, but One-Step had significantly lower bond strengths (P < 0.05) in the wet and overwet conditions.

Mechanics of active surfaces

Science.gov (United States)

Salbreux, Guillaume; Jülicher, Frank

2017-09-01

We derive a fully covariant theory of the mechanics of active surfaces. This theory provides a framework for the study of active biological or chemical processes at surfaces, such as the cell cortex, the mechanics of epithelial tissues, or reconstituted active systems on surfaces. We introduce forces and torques acting on a surface, and derive the associated force balance conditions. We show that surfaces with in-plane rotational symmetry can have broken up-down, chiral, or planar-chiral symmetry. We discuss the rate of entropy production in the surface and write linear constitutive relations that satisfy the Onsager relations. We show that the bending modulus, the spontaneous curvature, and the surface tension of a passive surface are renormalized by active terms. Finally, we identify active terms which are not found in a passive theory and discuss examples of shape instabilities that are related to active processes in the surface.

Effects of different surface-treatment methods on the bond strengths of resin cements to full-ceramic systems

Directory of Open Access Journals (Sweden)

Gülay Kansu

2011-09-01

Conclusions: The in vitro findings from this study indicate that surface-treatment procedures applied to the IPS Empress and the IPS Empress 2 full-ceramic systems are important when cement types are considered. In contrast, cement types and surface-treatment methods had no effect on changing the bond strength of the In-Ceram ceramic system.

Comparison of shear bond strength between unfilled resin to dry enamel and dentin bonding to moist and dry enamel

Directory of Open Access Journals (Sweden)

Yasini E.

2005-05-01

Full Text Available Statement of Problem: The use of dentine bondings on enamel and dentin in total etch protocols has recently become popular. Unfilled resin is hydrophobic and dentin bonding is hydrophilic in nature. This chemical difference could be effective in enamel bonding process. Purpose: The aim of this study was to compare the shear bond strength of unfilled resin to dry enamel and dentin bonding to dry and moist enamel. Materials and Methods: In this experimental study, a total of 30 incisor teeth were used. The specimens were randomly assigned to three groups of 10. 37% phosphoric acid etchant was applied to the enamel surfaces in each group for 15 seconds, rinsed with water for 20 seconds and dried for 20 seconds with compressed air in groups one and two. After conditioning, group 1 received unfilled resin (Margin Bond, Colten and group 2 received dentin bonding (Single Bond, 3M and in group 3 after conditioning and rinsing with water, a layer of dentin bonding (Single Bond was applied on wet enamel. The enamel and dentin bonding were light cured for 20 seconds. A ring mold 3.5 mm in diameter and 2 mm height was placed over the specimens to receive the composite filling material (Z100, 3M. The composite was cured for 40 seconds. The specimens were thermocycled and shear bond strengths were determined using an Instron Universal Testing Machine. The findings were analyzed by ANOVA One-Way and Tukey HSD tests. Results: Shear bond strength of dentin bonding to dry enamel was significantly less than unfilled resin to dry enamel (P<0.05. There was no significant difference between the bond strength of dentin bonding to moist and dry enamel. In addition bond strength of dentin bonding to wet enamel was not significantly different from unfilled resin to dry enamel. Conclusion: Based on the findings of this study, it is suggested that enamel surface should remain slightly moist after etching before bonding with single bond but when using unfilled resin, the

Z-H Bond Activation in (Di)hydrogen Bonding as a Way to Proton/Hydride Transfer and H2 Evolution.

Science.gov (United States)

Belkova, Natalia V; Filippov, Oleg A; Shubina, Elena S

2018-02-01

The ability of neutral transition-metal hydrides to serve as a source of hydride ion H - or proton H + is well appreciated. The hydride ligands possessing a partly negative charge are proton accepting sites, forming a dihydrogen bond, M-H δ- ⋅⋅⋅ δ+ HX (M=transition metal or metalloid). On the other hand, some metal hydrides are able to serve as a proton source and give hydrogen bond of M-H δ+ ⋅⋅⋅X type (X=organic base). In this paper we analyse recent works on transition-metal and boron hydrides showing i) how formation of an intermolecular complex between the reactants changes the Z-H (M-H and X-H) bond polarity and ii) what is the implication of such activation in the mechanisms of hydrides reactions. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Assessment and characterization of degradation effect for the varied degrees of ultra-violet radiation onto the collagen-bonded polypropylene non-woven fabric surfaces.

Science.gov (United States)

Tyan, Yu-Chang; Liao, Jiunn-Der; Klauser, Ruth; Wu, Ie-Der; Weng, Chih-Chiang

2002-01-01

Exposure to ultra-violet (UV)-C radiation is a frequently used method to prevent bacteria from invasion of blood-contact biomedical products. Potential damage induced by UV radiation to collagen is of concern due to the decay of bioactivity, considerably correlated with structural alterations. Our current investigation studies the collagen-bonded non-woven polypropylene (PP) fabric surface. In this experiment, antenna-coupling microwave plasma is utilized to activate PP fabric and then the sample is grafted with acrylic acid (AAc). Type III collagen is immobilized by using water soluble 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide as coupling agent. The collagen-bonded samples with sample temperature ca. 4 degrees C are then exposed to UV-254nm radiation for different time intervals. By using fourier-transformed infrared with attenuated total reflection (FTIR-ATR) and XPS (X-ray photoelectron spectroscopy), we examine the chemical structures of samples with different treatments. Coomassie brilliant blue G250 method is utilized to quantify the immobilized collagen on the PP fabric surfaces. Blood-clotting effects are evaluated by activated partial thromboplastin time, thrombin time, and fibrinogen concentration tests. By means of cell counter and scanning electron microscopy we count red blood cells and platelets adhesion in the modified porous matrix. Our experimental results have demonstrated that with pAAc-grafting of ca. 173 microg cm(-2) and immobilized collagen of 80.5+/-4.7 microg cm(-2), for human plasma incubated samples of various intervals of UV-254 nm radiation, fibrinogen concentration decreases in human plasma, while platelets and red blood cells adhesions increase before UV radiation. However, the required time for thrombination shows significant change for UV radiation exposure of less than 20 h (alpha = 0.05). The decay of bioactivity for the UV-irradiated, collagen-bonded surfaces is thus evaluated. Surface analyses indicate that the decrease of

Mechanical and Non-Destructive Study of CFRP Adhesive Bonds Subjected to Pre-Bond Thermal Treatment and De-Icing Fluid Contamination

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Paweł H. Malinowski

2018-04-01

Full Text Available Composite materials are commonly used in many branches of industry. One of the effective methods to join the carbon fibre reinforced polymer (CFRP parts includes the use of adhesives. There is a search on effective methods for quality assurance of bonded parts. In the research here reported the influence of surface pre-bond modification on the adhesive bonds of CFRP plates has been analyzed. Adherends surface modifications, to include defects affecting the bonding quality, were obtained through surface thermal treatment, surface contamination with de-icing fluid and a combination of both the previously described treatments. Characterization of bonded joints was performed by means of mechanical testing, ultrasounds and electromechanical impedance (EMI measurements. The study here proposed has also the aim to evaluate the ability of different destructive and non-destructive techniques to assess the quality of the bonds. While mechanical tests were strongly affected by the surface modifications, results obtained ultrasound and EMI test have demonstrate only a limited ability of these techniques to differentiate between the different samples. In fact, ultrasounds did not show any changes in the bondline, due to pre-bond modifications. However, this technique was able to detect delamination in CFRP for one of the samples thermally treated at 280 °C. Electromechanical impedance (EMI measurements showed similar behavior as mechanical tests for samples thermally treated at 260 °C and 280 °C, and for the sample whose surface modification was made with a combination of thermally and de-icing fluid treatments.

Proposal of new bonding technique 'Instantaneous Liquid Phase (ILP) Bonding'

International Nuclear Information System (INIS)

Zhang, Yue-Chang; Nakagawa, Hiroji; Matsuda, Fukuhisa.

1987-01-01

A new bonding technique named ''Instantaneous Liquid Phase (ILP) bonding'' suitable mainly for welding dissimilar materials was proposed by which instantaneous melting of one or two of the faying surfaces is utilized. The processes of ILP bonding are mainly consisted of three stages, namely the first stage forming thin liquid layer by rapid heating, the second stage joining both specimens by thin liquid layer, and the third stage cooling the specimens rapidly to avoid the formation of brittle layer. The welding temperatures of the specimens to be welded in ILP bonding are generally differentiated from each other. ILP bonding was applied for a variety of combinations of dissimilar materials of aluminum, aluminum alloys, titanium, titanium alloy, carbon steel, austenitic stainless steel, copper and tungsten, and for similar materials of stainless steel and nickel-base alloy. There were no microvoids in these welding joints, and the formation of brittle layer at the bonding interface was suppressed. The welded joints of Al + Ti, Cu + carbon steel and Cu + austenitic stainless steel showed the fracture in base metal having lower tensile strength. Further, the welded joints of Al + carbon steel, Al alloy + Ti, Al alloy + carbon steel or + austenitic stainless steel, Ti + carbon steel or + austenitic stainless steel showed better tensile properties in the comparison with diffusion welding. Furthermore, ILP bonding was available for welding same materials susceptible to hot cracking. Because of the existence of liquid layer, the welding pressure required was extremely low, and preparation of faying surface by simple tooling or polishing by no.80 emery paper was enough. The change in specimen length before and after welding was relatively little, only depending on the thickness of liquid layer. The welding time was very short, and thus high welding efficiency was obtained. (author)

Metal-organic cooperative catalysis in C-H and C-C bond activation and its concurrent recovery.

Science.gov (United States)

Park, Young Jun; Park, Jung-Woo; Jun, Chul-Ho

2008-02-01

The development of an efficient catalytic activation (cleavage) system for C-H and C-C bonds is an important challenge in organic synthesis, because these bonds comprise a variety of organic molecules such as natural products, petroleum oils, and polymers on the earth. Among many elegant approaches utilizing transition metals to activate C-H and C-C bonds facilely, chelation-assisted protocols based on the coordinating ability of an organic moiety have attracted great attention, though they have often suffered from the need for an intact coordinating group in a substrate. In this Account, we describe our entire efforts to activate C-H or C-C bonds adjacent to carbonyl groups by employing a new concept of metal-organic cooperative catalysis (MOCC), which enables the temporal installation of a 2-aminopyridyl group into common aldehydes or ketones in a catalytic way. Consequently, a series of new catalytic reactions such as alcohol hydroacylation, oxo-ester synthesis, C-C triple bond cleavage, hydrative dimerization of alkynes, and skeletal rearrangements of cyclic ketones was realized through MOCC. In particular, in the quest for an optimized MOCC system composed of a Wilkinson's catalyst (Ph 3P) 3RhCl and an organic catalyst (2-amino-3-picoline), surprising efficiency enhancements could be achieved when benzoic acid and aniline were introduced as promoters for the aldimine formation process. Furthermore, a notable accomplishment of C-C bond activation has been made using 2-amino-3-picoline as a temporary chelating auxiliary in the reactions of unstrained ketones with various terminal olefins and Wilkinson's catalyst. In the case of seven-membered cyclic ketones, an interesting ring contraction to five- or six-membered ones takes place through skeletal rearrangements initiated by the C-C bond activation of MOCC. On the other hand, the fundamental advances of these catalytic systems into recyclable processes could be achieved by immobilizing both metal and organic

Nanomagnets La0.8Pb0.2(Fe0.8Co0.2)O3 assembled with a bonded surface graphene oxide: sensitive for sensing small gas molecules.

Science.gov (United States)

Bhargav, K K; Ram, S; Majumder, S B

2012-04-01

Nanocrystallites La0.8Pb0.2(Fe0.8Co0.2)O3 (LPFC) when bonded through a surface layer (carbon) in small ensembles display surface sensitive magnetism useful for biological probes, electrodes, and toxic gas sensors. A simple dispersion and hydrolysis of the salts in ethylene glycol (EG) in water is explored to form ensembles of the nanocrystallites (NCs) by combustion of a liquid precursor gel slowly in microwave at 70-80 dgrees C (apparent) in a closed container in air. In a dilute sample, the EG molecules mediate hydrolyzed species to configure in small groups in process to form a gel. Proposed models describe how a residual carbon bridges a stable bonded layer of a graphene-oxide-like hybrid structure on the LPFC-NCs in attenuating the magnetic structure. SEM images, measured from a pelletized sample which was used to study the gas sensing features in terms of the electrical resistance, describe plate shaped NCs, typically 30-60 nm widths, 60-180 nm lengths and -50 m2/g surface area (after heating at -750 degrees C). These NCs are arranged in ensembles (200-900 nm size). As per the X-ray diffraction, the plates (a Pnma orthorhombic structure) bear only small strain -0.0023 N/m2 and oxygen vacancies. The phonon and electronic bands from a bonded surface layer disappear when it is etched out slowly by heating above 550 degrees C in air. The surface layer actively promotes selective H2 gas sensor properties.

Are Bonding Agents being Effective on the Shear Bond Strength of Orthodontic Brackets Bonded to the Composite?

Directory of Open Access Journals (Sweden)

Fahimeh Farzanegan

2014-06-01

Full Text Available Introduction: One of the clinical problems in orthodontics is the bonding of brackets tocomposite restorations. The aim of this study was to evaluate the shear bondstrength of brackets bonded to composite restorations using Excite. Methods:Forty brackets were bonded to composite surfaces, which were embedded inacrylic resin. One of the following four protocols was employed for surfacepreparation of the composite: group 1 37% phosphoric acid for 60 seconds, group2 roughening with a diamond bur plus 37% phosphoric acid for 60 seconds, group3 37% phosphoric acid for 60 seconds and the applying Excite®, group4 roughening with diamond bur plus 37% phosphoric acid for 60 seconds andapplying Excite®. Maxillary central brackets were bonded onto thecomposite prepared samples with Transbond XT. Shear Bond Strength (SBS wasmeasured by a universal testing machine. The ANOVA and Tukey test was utilizedfor data analysis. Results: There was a significant difference betweenthe four groups (P

The influence of ceramic surface treatments on the micro-shear bond strength of composite resin to IPS Empress 2.

Science.gov (United States)

Panah, Faride Gerami; Rezai, Sosan Mir Mohammad; Ahmadian, Leila

2008-07-01

An increasing demand for esthetic restorations has resulted in the development of new ceramic systems, but fracture of veneering ceramics still remains the primary cause of failure. Porcelain repair frequently involves replacement with composite resin, but the bond strength between composite resin and all-ceramic coping materials has not been studied extensively. The purpose of this study was to evaluate the influence of different ceramic surface treatments on the micro-shear bond strength of composite resin to IPS Empress 2 coping material. Sixteen 7 x 7 x 1 mm(3) lithia disilicate-based core ceramic plates were fabricated using the lost wax technique. The plates were divided into eight groups, and eight different surface treatments were performed: (1) no treatment (NT); (2) airborne-particle abrasion with 50-mum alumina particles (Al); (3) acid etching with 9.6% hydrofluoric acid for 1 min (HF); (4) silane coating (S); (5) AlHF; (6) AlS; (7) HFS; and (8) AlHFS. Then, ten composite resin cylinders (0.8-mm diameter x 0.5-mm height) were light-polymerized onto the ceramic plates in each group. Each specimen was subjected to a shear load at a crosshead speed of 0.5 mm/min until fracture occurred. The fracture sites were examined with scanning electron microscopy (SEM) to determine the location of failure during debonding and to examine the surface treatment effects. One-way analysis of variance (ANOVA) and multiple comparison (Dunnet T3) tests were used for statistical analysis of data. The mean micro-shear bond strength values (SD) in MPa were--NT: 4.10 (3.06), Al: 7.56 (4.11), HF: 14.04 (2.60), S: 14.58 (2.14), AlHF: 15.56 (3.36), AlS: 23.02 (4.17), HFS: 24.7 (4.43), AlHFS: 26.0 (3.71). ANOVA indicated the influence of surface treatment was significant (p Empress 2 was significantly different depending on the surface treatment method. Among the investigated methods, silane coating after airborne-particle abrasion and etching was the most effective surface treatment

Relationship between thin-film bond strength as measured by a scratch test, and indentation hardness for bonding agents.

Science.gov (United States)

Kusakabe, Shusuke; Rawls, H Ralph; Hotta, Masato

2016-03-01

To evaluate thin-film bond strength between a bonding agent and human dentin, using a scratch test, and the characteristics and accuracy of measurement. One-step bonding agents (BeautiBond; Bond Force; Adper Easy Bond; Clearfil tri-S Bond) and two-step bonding agents (Cleafil SE Bond; FL-Bond II) were investigated in this study. Flat dentin surfaces were prepared for extracted human molars. The dentin surfaces were ground and bonding agents were applied and light cured. The thin-film bond strength test of the specimens was evaluated by the critical load at which the coated bonding agent failed and dentin appeared. The scratch mark sections were then observed under a scanning electron microscope. Indentation hardness was evaluated by the variation in depth under an applied load of 10gf. Data were compared by one-way ANOVA with the Scheffé's post hoc multiple comparison test (pstrength and indentation hardness were analyzed using analysis of correlation and covariance. The thin-film bond strength of two-step bonding agents were found to be significantly higher than that of one-step bonding agents with small standard deviations. Scratch marks consistently showed adhesive failure in the vicinity of the bonding agent/dentin interface. The indentation hardness showed a trend that two-step bonding agents have greater hardness than one-step bonding agents. A moderately significant correlation (r(2)=0.31) was found between thin-film bond strength and indentation hardness. Thin-film bond strength test is a valid and reliable means of evaluating bond strength in the vicinity of the adhesive interface and is more accurate than other methods currently in use. Further, the thin-film bond strength is influenced by the hardness of the cued bonding agent. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Silanated Surface Treatment: Effects on the Bond Strength to Lithium Disilicate Glass-Ceramic.

Science.gov (United States)

Baratto, Samantha Schaffer Pugsley; Spina, Denis Roberto Falcão; Gonzaga, Carla Castiglia; Cunha, Leonardo Fernandes da; Furuse, Adilson Yoshio; Baratto Filho, Flares; Correr, Gisele Maria

2015-10-01

The aim of this study was to evaluate the effect of silanization protocols on the bond strength of two resin cements to a lithium disilicate glass-ceramic. Thirty-two ceramic discs were assigned to 2 groups (n=16): G1 - dual-cured resin cement and G2 - light-cured resin cement. Four subgroups were evaluated according to the used silanization protocol. The glass-ceramic was etched with 10% hydrofluoric acid for 20 s and silane was applied for 1 min, as follows: CTL - according to the manufacturer's instructions; HA - dried with hot air; NWA - washed and dried with water and air at room temperature; HWA - washed and dried with hot water and hot air. Thereafter, adhesive was applied and light-cured for 20 s. Silicon molds were used to prepare resin cement cylinders (1x1 mm) on the ceramic surface. The specimens were stored in deionized water at 37 °C for 48 h and subjected to a micro-shear test. The data were submitted to statistical analysis (?#61537;=0.05). Group G1 showed higher bond strengths than G2, except for the CTL and NWA subgroups. Differences as function of the silanization protocol were only observed in G1: HWA (25.13±6.83)≥HA (22.95±7.78)≥CTL(17.44±7.24) ≥NWA(14.63±8.76). For G2 there was no difference among the subgroups. In conclusion, the silanization protocol affected the resin cement/ceramic bond strengths, depending on the material. Washing/drying with hot water and/or hot air increased only the bond strength of the dual-cured resin cement.

30 CFR 800.21 - Collateral bonds.

Science.gov (United States)

2010-07-01

... 30 Mineral Resources 3 2010-07-01 2010-07-01 false Collateral bonds. 800.21 Section 800.21 Mineral... FOR SURFACE COAL MINING AND RECLAMATION OPERATIONS UNDER REGULATORY PROGRAMS § 800.21 Collateral bonds. (a) Collateral bonds, except for letters of credit, cash accounts, and real property, shall be...

New bonding configuration on Si(111) and Ge(111) surfaces induced by the adsorption of alkali metals

DEFF Research Database (Denmark)

Lottermoser, L.; Landemark, E.; Smilgies, D.M.

1998-01-01

The structure of the (3×1) reconstructions of the Si(111) and Ge(111) surfaces induced by adsorption of alkali metals has been determined on the basis of surface x-ray diffraction and low-energy electron diffraction measurements and density functional theory. The (3×1) surface results primarily f...... from the substrate reconstruction and shows a new bonding configuration consisting of consecutive fivefold and sixfold Si (Ge) rings in 〈11̅ 0〉 projection separated by channels containing the alkali metal atoms. © 1998 The American Physical Society...

Another way of looking at bonding on bimetallic surfaces: the role of spin polarization of surface metal d states

International Nuclear Information System (INIS)

Escano, M C; Nguyen, T Q; Nakanishi, H; Kasai, H

2009-01-01

The nature of electronic and chemical properties of an unstrained Pt monolayer on a 3d transition metal substrate, M (M = Cr, Mn, Fe), is studied using spin-polarized density functional theory calculations. High spin polarization of Pt d states is noted, verifying the magnetization induced on Pt, which is observed to be responsible for redirecting the analysis of bond formation on a metal surface towards a different perspective. While the shift in the Pt d band center (the average energy of the Pt d band, commonly used to predict the reactivity of surfaces) does give the expected trend in adsorbate (oxygen) chemisorption energy across the bimetallic surfaces in this work, our results show that for spin-polarized Pt d states, the variation in strength of adsorption with respect to the Fermi level density of states is more predictive of Pt chemisorption properties. Hence, this study introduces a scheme for analyzing trends in reactivity of bimetallic surfaces where adsorption energies are used as reactivity parameters and where spin polarization effects cannot be neglected. (fast track communication)

Shock-induced electrical activity in polymeric solids. A mechanically induced bond scission model

International Nuclear Information System (INIS)

Graham, R.A.

1979-01-01

When polymeric solids are subjected to high-pressure shock loading, two anomalous electrical phenomena, shock-induced conduction and shock-induced polarization, are observed. The present paper proposes a model of mechanically induced bond scission within the shock front to account for the effects. An experimental study of shock-induced polarization in poly(pyromellitimide) (Vespel SP-1) is reported for shock compressions from 17 to 23% (pressures from 2.5 to 5.4 GPa). Poly(pyromellitimide) is found to be a strong generator of such polarization and the polarization is found to reflect an irreversible or highly hysteretic process. The present measurements are combined with prior measurements to establish a correlation between monomer structure and strength of shock-induced polarization; feeble signals are observed in the simpler monomer repeat units of poly(tetrafluoroethylene) and polyethylene while the strongest signals are observed in more complex monomers of poly(methyl methacrylate) and poly(pyromellitimide). It is also noted that there is an apparent correlation between shock-induced conduction and shock-induced polarization. Such shock-induced electrical activity is also found to be well correlated with the propensity for mechanical bond scission observed in experiments carried out in conventional mechanochemical studies. The bond scission model can account for characteristics observed for electrical activity in shock-loaded polymers and their correlation to monomer structure. Localization of elastic energy within the monomer repeat unit or along the main chain leads to the different propensities for bond scission and resulting shock-induced electrical activity

Progress in cold roll bonding of metals

International Nuclear Information System (INIS)

Li Long; Nagai, Kotobu; Yin Fuxing

2008-01-01

Layered composite materials have become an increasingly interesting topic in industrial development. Cold roll bonding (CRB), as a solid phase method of bonding same or different metals by rolling at room temperature, has been widely used in manufacturing large layered composite sheets and foils. In this paper, we provide a brief overview of a technology using layered composite materials produced by CRB and discuss the suitability of this technology in the fabrication of layered composite materials. The effects of process parameters on bonding, mainly including process and surface preparation conditions, have been analyzed. Bonding between two sheets can be realized when deformation reduction reaches a threshold value. However, it is essential to remove surface contamination layers to produce a satisfactory bond in CRB. It has been suggested that the degreasing and then scratch brushing of surfaces create a strong bonding between the layers. Bonding mechanisms, in which the film theory is expressed as the major mechanism in CRB, as well as bonding theoretical models, have also been reviewed. It has also been showed that it is easy for fcc structure metals to bond compared with bcc and hcp structure metals. In addition, hardness on bonding same metals plays an important part in CRB. Applications of composites produced by CRB in industrial fields are briefly reviewed and possible developments of CRB in the future are also described. Corrections were made to the abstract and conclusion of this article on 18 June 2008. The corrected electronic version is identical to the print version. (topical review)

Bonding two surfaces by exposing to actinic radiation an epoxide liquid composition

International Nuclear Information System (INIS)

Green, G.E.

1981-01-01

A method for preparing a film adhesive from an epoxide resin is described. A liquid containing an epoxide resin and a photopolymerizable compound is polymerized to form a solid continuous film by exposure to actinide radiation. A catalyst can be used but no thermal crosslinking should be allowed to occur. The film so obtained is used to bond surfaces together by the application of heat and pressure. The period of heating can be very short, as there need be no solvent to evaporate and the films need not be thick, typically 20 to 250 μm. (O.T.)

Non-silicon substrate bonding mediated by poly(dimethylsiloxane) interfacial coating

Energy Technology Data Exchange (ETDEWEB)

Zhang, Hainan [Department of BioNano Technology, Gachon University, Gyeonggi-do 461-701 (Korea, Republic of); Lee, Nae Yoon, E-mail: nylee@gachon.ac.kr [Department of BioNano Technology, Gachon University, Gyeonggi-do 461-701 (Korea, Republic of); Gachon Medical Research Institute, Gil Medical Center, Inchon 405-760 (Korea, Republic of)

2015-02-01

Graphical abstract: Low-molecular-weight PDMS coating on the surfaces of non-silicon substrates such as thermoplastics ensures permanent sealing with a silicone elastomer, PDMS, simply by surface oxidization followed by ambient condition bonding, mediated by a robust siloxane bond formation at the interface. - Highlights: • Non-silicon thermoplastic was bonded with poly(dimethylsiloxane) silicone elastomer. • Low-molecular-weight PDMS interfacial layer was chemically coated on thermoplastic. • Bonding was realized by corona treatment and physical contact under ambient condition. • Bonding is universally applicable regardless of thermoplastic type and property. • Homogeneous PDMS-like microchannel was obtained inside the thermoplastic-PDMS microdevice. - Abstract: In this paper, we introduce a simple and robust strategy for bonding poly(dimethylsiloxane) (PDMS) with various thermoplastic substrates to fabricate a thermoplastic-based closed microfluidic device and examine the feasibility of using the proposed method for realizing plastic–plastic bonding. The proposed bonding strategy was realized by first coating amine functionality on an oxidized thermoplastic surface. Next, the amine-functionalized surface was reacted with a monolayer of low-molecular-weight PDMS, terminated with epoxy functionality, by forming a robust amine-epoxy bond. Both the PDMS-coated thermoplastic and PDMS were then oxidized and permanently assembled at 25 °C under a pressure of 0.1 MPa for 15 min, resulting in PDMS-like surfaces on all four inner walls of the microchannel. Surface characterizations were conducted, including water contact angle measurement, X-ray photoelectron spectroscopy (XPS), and fluorescence measurement, to confirm the successful coating of the thin PDMS layer on the plastic surface, and the bond strength was analyzed by conducting a peel test, burst test, and leakage test. Using the proposed method, we could successfully bond various thermoplastics such

A Raman spectroscopy study on the effects of intermolecular hydrogen bonding on water molecules absorbed by borosilicate glass surface

Science.gov (United States)

Li, Fabing; Li, Zhanlong; Wang, Ying; Wang, Shenghan; Wang, Xiaojun; Sun, Chenglin; Men, Zhiwei

2018-05-01

The structural forms of water/deuterated water molecules located on the surface of borosilicate capillaries have been first investigated in this study on the basis of the Raman spectral data obtained at different temperatures and under atmospheric pressure for molecules in bulk and also for molecules absorbed by borosilicate glass surface. The strongest two fundamental bands locating at 3063 cm-1 (2438 cm-1) in the recorded Raman spectra are assigned here to the Osbnd H (Osbnd D) bond stretching vibrations and they are compared with the corresponding bands observed at 3124 cm-1 (2325 cm-1) in the Raman spectrum of ice Ih. Our spectroscopic observations have indicated that the structure of water and deuterated water molecules on borosilicate surface is similar to that of ice Ih (hexagonal phase of ice). These observations have also indicated that water molecules locate on the borosilicate surface so as to construct a bilayer structure and that strong and weak intermolecular hydrogen bonds are formed between water/deuterated molecules and silanol groups on borosilicate surface. In accordance with these findings, water and deuterated water molecules at the interface of capillary have a higher melting temperature.

Shear bond strength of two bonding systems on dentin surfaces prepared with Er:YAG laser; Resistencia de uniao ao cisalhamento de dois sistemas adesivos em superficies dentinarias preparadas com laser de Er:YAG

Energy Technology Data Exchange (ETDEWEB)

Dall' Magro, Eduardo

2001-07-01

The purpose of this study was to examine the shear bond strength of two bonding dentin systems, one 'one step' (Single Bond - 3M) and one 'self-etching' (Prompt-L-ESPE), when applied on dentin surfaces prepared with Er:YAG laser (2,94{mu}m) that underwent ar not, acid etched. Forty one human molars just extracted were selected and after the cut with diamond disc and included in acrylic resin, resulting in 81 specimens (hemi crowns). After, the specimens were divided in one group treated with sand paper and another two groups treated with Er:YAG laser with 200 mJ and 250 mJ of energy and 2 Hz of frequency. Next, the prepared surfaces received three treatments with following application: 1) acid + Single Bond + Z 250 resin, 2) prompt-L-Pop + Z 250 resin, and 3) acid without, Single Bond + Z 250 resin. The Z 250 resin was applied and photopolymerized in increments on a Teflon matrix that belonged to an apparatus called 'Assembly Apparatus' machine producing cylinders of 3,5 mm of diameter and 5 mm of height. After these specimens were submitted to thermo cycling during 1 minute the 55 deg C and during 1 minute with 5 deg C with a total of 500 cycles for specimen, and the measures of shear bond strength were abstained using EMIC model DL 2000 rehearsed machine, with speed of 0,5 mm/min, measuring the final rupture tension (Mpa). The results showed an statistic superiority of 5% of probability level in dentin flattened with sandpaper and with laser using 200 mJ of energy with aspect to the ones flattened with laser using 250 mJ of energy. It was observed that using 'Single Bond' bonding dentin system the marks were statistically superior at 5% of probability with reference to the use of the Prompt-L-Pop adhesive system. So, it was concluded that Er:YAG Laser with 200 mJ of energy produced similar dentin cavity prepare than sandpaper and Single Bond seemed the best bonding agent system between restorative material and dentin

Shear bond strength of veneering porcelain to zirconia: Effect of surface treatment by CNC-milling and composite layer deposition on zirconia.

Science.gov (United States)

Santos, R L P; Silva, F S; Nascimento, R M; Souza, J C M; Motta, F V; Carvalho, O; Henriques, B

2016-07-01

The purpose of this study was to evaluate the shear bond strength of veneering feldspathic porcelain to zirconia substrates modified by CNC-milling process or by coating zirconia with a composite interlayer. Four types of zirconia-porcelain interface configurations were tested: RZ - porcelain bonded to rough zirconia substrate (n=16); PZ - porcelain bonded to zirconia substrate with surface holes (n=16); RZI - application of a composite interlayer between the veneering porcelain and the rough zirconia substrate (n=16); PZI - application of a composite interlayer between the porcelain and the zirconia substrate treated by CNC-milling (n=16). The composite interlayer was composed of zirconia particles reinforced porcelain (30%, vol%). The mechanical properties of the ceramic composite have been determined. The shear bond strength test was performed at 0.5mm/min using a universal testing machine. The interfaces of fractured and untested specimens were examined by FEG-SEM/EDS. Data was analyzed with Shapiro-Wilk test to test the assumption of normality. The one-way ANOVA followed by Tukey HSD multiple comparison test was used to compare shear bond strength results (α=0.05). The shear bond strength of PZ (100±15MPa) and RZI (96±11MPa) specimens were higher than that recorded for RZ (control group) specimens (89±15MPa), although not significantly (p>0.05). The highest shear bond strength values were recorded for PZI specimens (138±19MPa), yielding a significant improvement of 55% relative to RZ specimens (p<0.05). This study shows that it is possible to highly enhance the zirconia-porcelain bond strength - even by ~55% - by combining surface holes in zirconia frameworks and the application of a proper ceramic composite interlayer. Copyright © 2016 Elsevier Ltd. All rights reserved.

Dangling bonds and crystalline inclusions in amorphous materials

Energy Technology Data Exchange (ETDEWEB)

Ferrari, L [Ferrara Univ. (Italy). Ist. di Matematica; Russo, G [Bologna Univ. (Italy). Ist. di Fisica

1981-02-07

It is suggested that on the surface of crystalline inclusions dangling bond formation is favoured due to unbalanced local stresses. The energy for bond tearings is probably originated from the exothermic process leading to the crystalline inclusion configuration which is more stable than the original amorphous one. A thermodynamical calculation is performed giving the ratio nsub(k) of crystalline inclusions having k dangling bonds on their surface.

Multiple C-H Bond Activations and Ring-Opening C-S Bond Cleavage of Thiophene by Dirhenium Carbonyl Complexes.

Science.gov (United States)

Adams, Richard D; Dhull, Poonam; Tedder, Jonathan D

2018-06-14

The reaction of Re 2 (CO) 8 (μ-C 6 H 5 )(μ-H) (1) with thiophene in CH 2 Cl 2 at 40 °C yielded the new compound Re 2 (CO) 8 (μ-η 2 -SC 4 H 3 )(μ-H) (2), which contains a bridging σ-π-coordinated thienyl ligand formed by the activation of the C-H bond at the 2 position of the thiophene. Compound 2 exhibits dynamical activity on the NMR time scale involving rearrangements of the bridging thienyl ligand. The reaction of compound 2 with a second 1 equiv of 1 at 45 °C yielded the doubly metalated product [Re 2 (CO) 8 (μ-H)] 2 (μ-η 2 -2,3-μ-η 2 -4,5-C 4 H 2 S) (3), formed by the activation of the C-H bond at the 5 position of the thienyl ligand in 2. Heating 3 in a hexane solvent to reflux transformed it into the ring-opened compound Re(CO) 4 [μ-η 5 -η 2 -SCC(H)C(H)C(H)][Re(CO) 3 ][Re 2 (CO) 8 (μ-H)] (4) by the loss of one CO ligand. Compound 4 contains a doubly metalated 1-thiapentadienyl ligand formed by the cleavage of one of the C-S bonds. When heated to reflux (125 °C) in an octane solvent in the presence of H 2 O, the new compound Re(CO) 4 [η 5 -μ-η 2 -SC(H)C(H)C(H)C(H)]Re(CO) 3 (5) was obtained by cleavage of the Re 2 (CO) 8 (μ-H) group from 4 with formation of the known coproduct [Re(CO) 3 (μ 3 -OH)] 4 . All new products were characterized by single-crystal X-ray diffraction analyses.

Improvement of bonding properties of laser transmission welded, dissimilar thermoplastics by plasma surface treatment

Energy Technology Data Exchange (ETDEWEB)

Hopmann, Ch.; Weber, M.; Schöngart, M.; Sooriyapiragasam, S.; Behm, H.; Dahlmann, R. [Institute of Plastics Processing (IKV), RWTH Aachen University, Pontstrasse 49, 52062 Aachen (Germany)

2015-05-22

Compared to different welding methods such as ultrasonic welding, laser transmission welding is a relatively new technology to join thermoplastic parts. The most significant advantages over other methods are the contactless energy input which can be controlled very precisely and the low mechanical loads on the welded parts. Therefore, laser transmission welding is used in various areas of application, for example in medical technology or for assembling headlights in the automotive sector. However, there are several challenges in welding dissimilar thermoplastics. This may be due to different melting points on the one hand and different polarities on the other hand. So far these problems are faced with the intermediate layer technique. In this process a layer bonding together the two components is placed between the components. This means that an additional step in the production is needed to apply the extra layer. To avoid this additional step, different ways of joining dissimilar thermoplastics are investigated. In this regard, the improvement in the weldability of the dissimilar thermoplastics polyamide 6 (PA 6) and polypropylene (PP) by means of plasma surface modification and contour welding is examined. To evaluate the influence of the plasma surface modification process on the subsequent welding process of the two dissimilar materials, the treatment time as well as the storage time between treatment and welding are varied. The treatment time in pulsed micro wave excited oxygen plasmas with an electron density of about 1x10{sup 17} m{sup −3} is varied from 0.5 s to 120 s and the time between treatment and welding is varied from a few minutes up to a week. As reference, parts being made of the same polymer (PP and PA 6) are welded and tested. For the evaluation of the results of the welding experiments, short-time tensile tests are used to determine the bond strength. Without plasma treatment the described combination of PA 6/PP cannot be welded with

Improvement of bonding properties of laser transmission welded, dissimilar thermoplastics by plasma surface treatment

International Nuclear Information System (INIS)

Hopmann, Ch.; Weber, M.; Schöngart, M.; Sooriyapiragasam, S.; Behm, H.; Dahlmann, R.

2015-01-01

Compared to different welding methods such as ultrasonic welding, laser transmission welding is a relatively new technology to join thermoplastic parts. The most significant advantages over other methods are the contactless energy input which can be controlled very precisely and the low mechanical loads on the welded parts. Therefore, laser transmission welding is used in various areas of application, for example in medical technology or for assembling headlights in the automotive sector. However, there are several challenges in welding dissimilar thermoplastics. This may be due to different melting points on the one hand and different polarities on the other hand. So far these problems are faced with the intermediate layer technique. In this process a layer bonding together the two components is placed between the components. This means that an additional step in the production is needed to apply the extra layer. To avoid this additional step, different ways of joining dissimilar thermoplastics are investigated. In this regard, the improvement in the weldability of the dissimilar thermoplastics polyamide 6 (PA 6) and polypropylene (PP) by means of plasma surface modification and contour welding is examined. To evaluate the influence of the plasma surface modification process on the subsequent welding process of the two dissimilar materials, the treatment time as well as the storage time between treatment and welding are varied. The treatment time in pulsed micro wave excited oxygen plasmas with an electron density of about 1x10 17 m −3 is varied from 0.5 s to 120 s and the time between treatment and welding is varied from a few minutes up to a week. As reference, parts being made of the same polymer (PP and PA 6) are welded and tested. For the evaluation of the results of the welding experiments, short-time tensile tests are used to determine the bond strength. Without plasma treatment the described combination of PA 6/PP cannot be welded with sufficient bond

Influence of Er,Cr:YSGG Laser Surface Treatments on Micro Push-Out Bond Strength of Fiber Posts to Composite Resin Core Materials

Directory of Open Access Journals (Sweden)

Mehrsima Ghavami-Lahiji

2018-03-01

Full Text Available Statement of problem: The bonding of fiber post to resin core or root dentin is challenged by limited penetration of resin material to the polymeric matrix of fiber posts. Objectives: The purpose of this study was to investigate the effect of Er,Cr:YSGG on micro push-out bond strength of glass fiber posts to resin core material. Materials and Methods: We used 2 commercially available fiber posts, Exacto (Angelus and White Post DC (FGM, which had similar coronal diameters. Specimens of each fiber post (n=36 were randomly divided into three subgroups (n=12 posts per group according to different surface treatment methods: control (no surface treatment, irradiation by 1W Er,Cr:YSGG, and irradiation by 1.5W Er,Cr:YSGG. A cylindrical plastic tube was placed around the post. Resin core material was filled into the tube and cured. Coronal portions of the posts were sectioned into 1-mm-thick slices. Then, the specimens were subjected to a thermocyling device for 3000 cycles. The micro push-out test was carried out using a Universal Testing Machine. Data were analyzed using one-way ANOVA followed by Tukey’s HSD post hoc test to investigate the effect of different surface treatments on each type of fiber post. Results: The 1.5W Er,Cr:YSGG laser statistically reduced micro push-out bond strength values in the Exacto groups (P0.05. Mode of failure analysis showed that mixed failure was the predominant failure type for all surface treatment groups. Conclusions: The beneficial effect of Er,Cr:YSGG laser application could not be confirmed based on the results of this in vitro study. Er,Cr:YSGG laser could not significantly enhance the bond strength values. However, the 1.5W laser statistically decreased micro push-out bond strength in the Exacto fiber posts.

1.3 μm wavelength vertical cavity surface emitting laser fabricated by orientation-mismatched wafer bonding: A prospect for polarization control

Science.gov (United States)

Okuno, Yae L.; Geske, Jon; Gan, Kian-Giap; Chiu, Yi-Jen; DenBaars, Steven P.; Bowers, John E.

2003-04-01

We propose and demonstrate a long-wavelength vertical cavity surface emitting laser (VCSEL) which consists of a (311)B InP-based active region and (100) GaAs-based distributed Bragg reflectors (DBRs), with an aim to control the in-plane polarization of output power. Crystal growth on (311)B InP substrates was performed under low-migration conditions to achieve good crystalline quality. The VCSEL was fabricated by wafer bonding, which enables us to combine different materials regardless of their lattice and orientation mismatch without degrading their quality. The VCSEL was polarized with a power extinction ratio of 31 dB.

The conserved His8 of the Moloney murine leukemia virus Env SU subunit directs the activity of the SU-TM disulphide bond isomerase

International Nuclear Information System (INIS)

Li Kejun; Zhang, Shujing; Kronqvist, Malin; Ekstroem, Maria; Wallin, Michael; Garoff, Henrik

2007-01-01

Murine leukemia virus (MLV) fusion is controlled by isomerization of the disulphide bond between the receptor-binding surface (SU) and fusion-active transmembrane subunits of the Env-complex. The bond is in SU linked to a CXXC motif. This carries a free thiol that upon receptor binding can be activated (ionized) to attack the disulphide and rearrange it into a disulphide isomer within the motif. To find out whether His8 in the conserved SPHQ sequence of Env directs thiol activation, we analyzed its ionization in MLV vectors with wtEnv and Env with His8 deleted or substituted for Tyr or Arg, which partially or completely arrests fusion. The ionization was monitored by following the pH effect on isomerization in vitro by Ca 2+ depletion or in vivo by receptor binding. We found that wtEnv isomerized optimally at slightly basic pH whereas the partially active mutant required higher and the inactive mutants still higher pH. This suggests that His8 directs the ionization of the CXXC thiol

77 FR 15378 - Agency Information Collection Activities: Application for Withdrawal of Bonded Stores for Fishing...

Science.gov (United States)

2012-03-15

... Activities: Application for Withdrawal of Bonded Stores for Fishing Vessels and Certificate of Use AGENCY: U... information collection request to the Office of Management and Budget (OMB) for review and approval in accordance with the Paperwork Reduction Act: Application for Withdrawal of Bonded Stores for Fishing Vessels...

Recent Advances in Adhesive Bonding - The Role of Biomolecules, Nanocompounds, and Bonding Strategies in Enhancing Resin Bonding to Dental Substrates.

Science.gov (United States)

Münchow, Eliseu A; Bottino, Marco C

2017-09-01

To present an overview on the main agents (i.e., biomolecules and nanocompounds) and/or strategies currently available to amplify or stabilize resin-dentin bonding. According to studies retrieved for full text reading (2014-2017), there are currently six major strategies available to overcome resin-dentin bond degradation: (i) use of collagen crosslinking agents, which may form stable covalent bonds with collagen fibrils, thus strengthening the hybrid layer; (ii) use of antioxidants, which may allow further polymerization reactions over time; (iii) use of protease inhibitors, which may inhibit or inactivate metalloproteinases; (iv) modification of the bonding procedure, which may be performed by using the ethanol wet-bonding technique or by applying an additional adhesive (hydrophobic) coating, thereby strengthening the hybrid layer; (v) laser treatment of the substrate prior to bonding, which may cause specific topographic changes in the surface of dental substrates, increasing bonding efficacy; and (vi) reinforcement of the resin matrix with inorganic fillers and/or remineralizing agents, which may positively enhance physico-mechanical properties of the hybrid layer. With the present review, we contributed to the better understanding of adhesion concepts and mechanisms of resin-dentin bond degradation, showing the current prospects available to solve that problematic. Also, adhesively-bonded restorations may be benefited by the use of some biomolecules, nanocompounds or alternative bonding strategies in order to minimize bond strength degradation.

The effect of different surface treatments on the bond strength of a gingiva-colored indirect composite veneering material to three implant framework materials.

Science.gov (United States)

Koizuka, Mai; Komine, Futoshi; Blatz, Markus B; Fushiki, Ryosuke; Taguchi, Kohei; Matsumura, Hideo

2013-09-01

To evaluate and compare the shear-bond strength of a gingiva-colored indirect composite material to three different implant framework materials (zirconia ceramics, gold alloy, and titanium), and to investigate the effect of surface pretreatment by air-particle abrasion and four priming agents. A gingiva-colored indirect composite (Ceramage) was bonded to three framework materials (n = 80): commercially pure titanium (CP- Ti ), ADA (American Dental Association)-type 4 casting gold alloy (Type IV), and zirconia ceramics (Zirconia) with or without airborne-particle abrasion. Before bonding, the surface of the specimens was treated using no (control) or one of four priming agents: Alloy Primer (ALP), Estenia Opaque Primer (EOP), Metal Link Primer (MLP), and V-Primer (VPR). Shear-bond strength was determined after 24-h wet storage. Data were analyzed using Steel-Dwass for multiple comparisons, and Mann-Whitney U-test (P = 0.05). For both CP- Ti and Zirconia substrates, three groups, ALP, EOP, and MLP, showed significantly higher bond strengths (P composite material to commercially pure titanium and zirconia frameworks. Combined use of a thione monomer with a phosphoric monomer enhances the bond strengths to airborne-particle abraded type IV gold alloy. © 2012 John Wiley & Sons A/S.

Passive characterization and active testing of epoxy bonded regenerators for room temperature magnetic refrigeration

DEFF Research Database (Denmark)

Lei, Tian; Navickaité, Kristina; Engelbrecht, Kurt

2017-01-01

-layer AMR based on spherical particles is tested actively in a small reciprocating magnetic refrigerator, achieving a no-load temperature span of 16.8 °C using about 143 g of epoxy-bonded La(Fe,Mn,Si)13Hy materials. Simulations based on a one-dimensional (1D) AMR model are also implemented to validate......Epoxy bonded regenerators of both spherical and irregular La(Fe,Mn,Si)13Hy particles have been developed aiming at increasing the mechanical strength of active magnetic regenerators (AMR) loaded with brittle magnetocaloric materials and improving the flexibility of shaping the regenerator geometry....... Although the magnetocaloric properties of these materials are well studied, the flow and heat transfer characteristics of the epoxy bonded regenerators have seldom been investigated. This paper presents a test apparatus that passively characterizes regenerators using a liquid heat transfer fluid...

Effect of Various Surface Treatment on Repair Strength of Composite Resin

Directory of Open Access Journals (Sweden)

Y. Alizade

2004-12-01

Full Text Available Statement of Problem: In some clinical situations, repair of composite restorations is treatment of choice. Improving the bond strength between one new and old composite usually requires increased surface roughness to promote mechanical interlocking sincechemical bonding might not be adequate. Similarly, the treatment of a laboratory fabricated resin composite restoration involves the same procedures, and there is a need to create the strongest possible bond of a resin cement to a previously polymerized composite.Purpose: The aim of this study was to evaluate the effect of various surface treatments on the shear bond strength of repaired to aged composite resin.Materials and Methods: Eighty four cylindrical specimens of a composite resin were fabricated and stored in distilled water for 100 days prior to surface treatment. Surface treatment of old composite was done in 6 groups as follow:1- Air abrasion with CoJet sand particles with micoretcher + silane + dentin bonding agent2- Air abrasion with 50μm Al2O3 particles+ phosphoric acid+ silane+ dentin bonding agent3- Air abrasion with 50μm Al2O3 particles + phosphoric acid + dentin bonding agent4- Diamond bur + phosphoric acid + silane + dentin bonding agent5- Diamond bur + phosphoric acid + dentin bonding agent6- Diamond bur + phosphoric acid + composite activator + dentin bonding agentThen fresh composite resin was bonded to treated surfaces. Twelve specimens were also fabricated as control group with the same diameter but with the height twice as much as other specimens. All of the specimens were thermocycled prior to testing for shear bondstrength. The bond strength data were analyzed statistically using one way ANOVA test, t test and Duncan's grouping test.Results: One-way ANOVA indicated no significant difference between 7 groups (P=0.059. One-way ANOVA indicated significant difference between the three diamond bur groups (P=0.036. Silane had a significant effect on the repair bond

Comparative evaluation of shear bond strength of metallic brackets bonded with two different bonding agents under dry conditions and with saliva contamination.

Science.gov (United States)

Khanehmasjedi, Mashallah; Naseri, Mohammad Ali; Khanehmasjedi, Samaneh; Basir, Leila

2017-02-01

This study compared the shear bond strength of metallic brackets bonded with Single Bond and Assure bonding agents under dry and saliva-contamination conditions. Sixty sound premolar teeth were selected, and stainless-steel brackets were bonded on enamel surfaces with Single Bond and Assure bonding agents under dry condition or with saliva contamination. Shear bond strength values of brackets were measured in a universal testing machine. The adhesive remnant index scores were determined after debonding of the brackets under a stereomicroscope. One-way analysis of variance (ANOVA) was used to analyze bond strength. Two-by-two comparisons were made with post hoc Tukey tests (pbrackets to tooth structure were 9.29±8.56 MPa and 21.25±8.93 MPa with the use of Assure resin bonding agent under saliva-contamination and dry conditions, respectively. These values were 10.13±6.69 MPa and 14.09±6.6 MPa, respectively, under the same conditions with the use of Single Bond adhesive. Contamination with saliva resulted in a significant decrease in the bond strength of brackets to tooth structure with the application of Assure adhesive resin (pbrackets to tooth structures. Contamination with saliva significantly decreased the bond strength of Assure bonding agent compared with dry conditions. Copyright © 2016. Published by Elsevier Taiwan LLC.

Native lignin for bonding fiber boards - evaluation of bonding mechanisms in boards made from laccase-treated fibers of beech (Fagus sylvatica)

DEFF Research Database (Denmark)

Felby, Claus; Thygesen, Lisbeth Garbrecht; Sanadi, Anand

2004-01-01

indicate that lignin extractives are precipitated on the fiber surfaces. The improved bonding may be related to several factors, linked to a more lignin rich fiber surface, such as surface molecular entanglements and covalent bonding between fibers through cross-linking of radicals. (C) 2004 Published......The auto-adhesion of beech wood (Fagus sylvatica) fibers can be enhanced by a pretreatment of the fibers with a phenol oxidase enzyme. The mechanism of enzymatic catalyzed bonding is linked to the generation of stable radicals in lignin by oxidation. Fiberboards made from laccase-treated fibers...

Simulation of the effect of hydrogen bonds on water activity of glucose and dextran using the Veytsman model.

Science.gov (United States)

De Vito, Francesca; Veytsman, Boris; Painter, Paul; Kokini, Jozef L

2015-03-06

Carbohydrates exhibit either van der Waals and ionic interactions or strong hydrogen bonding interactions. The prominence and large number of hydrogen bonds results in major contributions to phase behavior. A thermodynamic framework that accounts for hydrogen bonding interactions is therefore necessary. We have developed an extension of the thermodynamic model based on the Veytsman association theory to predict the contribution of hydrogen bonds to the behavior of glucose-water and dextran-water systems and we have calculated the free energy of mixing and its derivative leading to chemical potential and water activity. We compared our calculations with experimental data of water activity for glucose and dextran and found excellent agreement far superior to the Flory-Huggins theory. The validation of our calculations using experimental data demonstrated the validity of the Veytsman model in properly accounting for the hydrogen bonding interactions and successfully predicting water activity of glucose and dextran. Our calculations of the concentration of hydrogen bonds using the Veytsman model were instrumental in our ability to explain the difference between glucose and dextran and the role that hydrogen bonds play in contributing to these differences. The miscibility predictions showed that the Veytsman model is also able to correctly describe the phase behavior of glucose and dextran. Copyright © 2014 Elsevier Ltd. All rights reserved.

Bond strength of three luting agents to zirconia ceramic - influence of surface treatment and thermocycling

Directory of Open Access Journals (Sweden)

Ahmed Attia

2011-08-01

Full Text Available OBJECTIVE: This in vitro study aimed to evaluate the influence of different surface treatments, 3 luting agents and thermocycling on microtensile bond strength (µTBS to zirconia ceramic. Material and METHODS: A total of 18 blocks (5x5x4 mm were fabricated from zirconia ceramic (ICE Zirkonia and duplicated into composite blocks (Alphadent. Ceramic blocks were divided into 3 groups (n=6 according to the following surface treatments: airborne-particle abrasion (AA, silica-coating, (SC (CoJet and silica coating followed by silane application (SCSI (ESPE Sil. Each group was divided into 3 subgroups (n=2 according to the 3 luting agents used. Resin-modified glass-ionomer cement (RMGIC, Ketac Cem Plus, self-adhesive resin cement (UN, RelyX Unicem and adhesive resin cement (ML, MultiLink Automix were used for bonding composite and zirconia blocks. Each bonding assembly was cut into microbars (10 mm long and 1±0.1 mm². Seven specimens of each subgroup were stored in water bath at 37ºC for 1 week. The other 7 specimens were stored in water bath at 37ºC for 30 days then thermocycled (TC for 7,500 cycles. µTBS values were recorded for each specimen using a universal testing machine. Statistical analyses were performed using a 3-way ANOVA model followed by serial 1-way ANOVAs. Comparison of means was performed with Tukey's HSD test at (α=0.05. RESULTS: µTBS ranged from 16.8 to 31.8 MPa after 1 week and from 7.3 to 16.4 MPa after 30 days of storage in water and thermocycling. Artificial aging significantly decreased µTBS (p<0.05. Considering surface treatment, SCSI significantly increased µTBS (p<0.05 compared to SC and AA. Resin cements (UN and ML demonstrated significantly higher µTBS (p<0.05 compared to RMGIC cement. CONCLUSIONS: Silica coating followed by silane application together with adhesive resin cements significantly increased µTBS, while thermocycling significantly decreased µTBS.

Shear bond strength of self-etch and total-etch bonding systems at different dentin depths

Directory of Open Access Journals (Sweden)

Ana Carolina Maito Villela-Rosa

2011-04-01

Full Text Available The purpose of this study was to evaluate the dentin shear bond strength of four adhesive systems (Adper Single Bond 2, Adper Prompt L-Pop, Magic Bond DE and Self Etch Bond in regards to buccal and lingual surfaces and dentin depth. Forty extracted third molars had roots removed and crowns bisected in the mesiodistal direction. The buccal and lingual surfaces were fixed in a PVC/acrylic resin ring and were divided into buccal and lingual groups assigned to each selected adhesive. The same specimens prepared for the evaluation of superficial dentin shear resistance were used to evaluate the different depths of dentin. The specimens were identified and abraded at depths of 0.5, 1.0, 1.5 and 2.0 mm. Each depth was evaluated by ISO TR 11405 using an EMIC-2000 machine regulated at 0.5 mm/min with a 200 Kgf load cell. We performed statistical analyses on the results (ANOVA, Tukey and Scheffé tests. Data revealed statistical differences (p < 0.01 in the adhesive and depth variation as well as adhesive/depth interactions. The Adper Single Bond 2 demonstrated the highest mean values of shear bond strength. The Prompt L-Pop product, a self-etching adhesive, revealed higher mean values compared with Magic Bond DE and Self Etch Bond adhesives, a total and self-etching adhesive respectively. It may be concluded that the shear bond strength of dentin is dependent on material (adhesive system, substrate depth and adhesive/depth interaction.

Low-temperature wafer-level gold thermocompression bonding: modeling of flatness deviations and associated process optimization for high yield and tough bonds

Science.gov (United States)

Stamoulis, Konstantinos; Tsau, Christine H.; Spearing, S. Mark

2005-01-01

Wafer-level, thermocompression bonding is a promising technique for MEMS packaging. The quality of the bond is critically dependent on the interaction between flatness deviations, the gold film properties and the process parameters and tooling used to achieve the bonds. The effect of flatness deviations on the resulting bond is investigated in the current work. The strain energy release rate associated with the elastic deformation required to overcome wafer bow is calculated. A contact yield criterion is used to examine the pressure and temperature conditions required to flatten surface roughness asperities in order to achieve bonding over the full apparent area. The results are compared to experimental data of bond yield and toughness obtained from four-point bend delamination testing and microscopic observations of the fractured surfaces. Conclusions from the modeling and experiments indicate that wafer bow has negligible effect on determining the variability of bond quality and that the well-bonded area is increased with increasing bonding pressure. The enhanced understanding of the underlying deformation mechanisms allows for a better controlled trade-off between the bonding pressure and temperature.

Shear bond strength of porcelain laminate veneers to enamel, dentine and enamel-dentine complex bonded with different adhesive luting systems.

Science.gov (United States)

Öztürk, Elif; Bolay, Şükran; Hickel, Reinhard; Ilie, Nicoleta

2013-02-01

The aim of this study was to evaluate the shear bond strength of porcelain laminate veneers to 3 different surfaces by means of enamel, dentine, and enamel-dentine complex. One hundred thirty-five extracted human maxillary central teeth were used, and the teeth were randomly divided into 9 groups (n=15). The teeth were prepared with 3 different levels for bonding surfaces of enamel (E), dentine (D), and enamel-dentine complex (E-D). Porcelain discs (IPS e.max Press, Ivoclar Vivadent) of 2mm in thickness and 4mm in diameter were luted to the tooth surfaces by using 2 light-curing (RelyX Veneer [RV], 3M ESPE; Variolink Veneer [VV], Ivoclar Vivadent) and a dual-curing (Variolink II [V2], Ivoclar Vivadent) adhesive systems according to the manufacturers' instructions. Shear bond strength test was performed in a universal testing machine at 0.5mm/min until bonding failure. Failure modes were determined under a stereomicroscope, and fracture surfaces were evaluated with a scanning electron microscope. The data were statistically analysed (SPSS 17.0) (p=0.05). Group RV-D exhibited the lowest bond strength value (5.42±6.6MPa). There was statistically no difference among RV-D, V2-D (13.78±8.8MPa) and VV-D (13.84±6.2MPa) groups (p>0.05). Group VV-E exhibited the highest bond strength value (24.76±8.8MPa). The type of tooth structure affected the shear bond strength of the porcelain laminate veneers to the 3 different types of tooth structures (enamel, dentine, and enamel-dentine complex). When dentine exposure is necessary during preparation, enough sound enamel must be protected as much as possible to maintain a good bonding; to obtain maximum bond strength, preparation margins should be on sound enamel. Copyright © 2012 Elsevier Ltd. All rights reserved.

CD44 Binding to Hyaluronic Acid Is Redox Regulated by a Labile Disulfide Bond in the Hyaluronic Acid Binding Site.

Directory of Open Access Journals (Sweden)

Helena Kellett-Clarke

Full Text Available CD44 is the primary leukocyte cell surface receptor for hyaluronic acid (HA, a component of the extracellular matrix. Enzymatic post translational cleavage of labile disulfide bonds is a mechanism by which proteins are structurally regulated by imparting an allosteric change and altering activity. We have identified one such disulfide bond in CD44 formed by Cys77 and Cys97 that stabilises the HA binding groove. This bond is labile on the surface of leukocytes treated with chemical and enzymatic reducing agents. Analysis of CD44 crystal structures reveal the disulfide bond to be solvent accessible and in the-LH hook configuration characteristic of labile disulfide bonds. Kinetic trapping and binding experiments on CD44-Fc chimeric proteins show the bond is preferentially reduced over the other disulfide bonds in CD44 and reduction inhibits the CD44-HA interaction. Furthermore cells transfected with CD44 no longer adhere to HA coated surfaces after pre-treatment with reducing agents. The implications of CD44 redox regulation are discussed in the context of immune function, disease and therapeutic strategies.

Mechanistic Insights on C-O and C-C Bond Activation and Hydrogen Insertion during Acetic Acid Hydrogenation Catalyzed by Ruthenium Clusters in Aqueous Medium

Energy Technology Data Exchange (ETDEWEB)

Shangguan, Junnan; Olarte, Mariefel V.; Chin, Ya-Huei [Cathy

2016-06-07

Catalytic pathways for acetic acid (CH3COOH) and hydrogen (H2) reactions on dispersed Ru clusters in the aqueous medium and the associated kinetic requirements for C-O and C-C bond cleavages and hydrogen insertion are established from rate and isotopic assessments. CH3COOH reacts with H2 in steps that either retain its carbon backbone and lead to ethanol, ethyl acetate, and ethane (47-95 %, 1-23 %, and 2-17 % carbon selectivities, respectively) or break its C-C bond and form methane (1-43 % carbon selectivities) at moderate temperatures (413-523 K) and H2 pressures (10-60 bar, 298 K). Initial CH3COOH activation is the kinetically relevant step, during which CH3C(O)-OH bond cleaves on a metal site pair at Ru cluster surfaces nearly saturated with adsorbed hydroxyl (OH*) and acetate (CH3COO*) intermediates, forming an adsorbed acetyl (CH3CO*) and hydroxyl (OH*) species. Acetic acid turnover rates increase proportionally with both H2 (10-60 bar) and CH3COOH concentrations at low CH3COOH concentrations (<0.83 M), but decrease from first to zero order as the CH3COOH concentration and the CH3COO* coverages increase and the vacant Ru sites concomitantly decrease. Beyond the initial CH3C(O)-OH bond activation, sequential H-insertions on the surface acetyl species (CH3CO*) lead to C2 products and their derivative (ethanol, ethane, and ethyl acetate) and the competitive C-C bond cleavage of CH3CO* causes the eventual methane formation. The instantaneous carbon selectivities towards C2 species (ethanol, ethane, and ethyl acetate) increase linearly with the concentration of proton-type Hδ+ (derived from carboxylic acid dissociation) and chemisorbed H*. The selectivities towards C2 products decrease with increasing temperature, because of higher observed barriers for C-C bond cleavage than H-insertion. This study offers an interpretation of mechanism and energetics and provides kinetic evidence of carboxylic acid assisted proton-type hydrogen (Hδ+) shuffling during H

Low temperature thermocompression bonding between aligned carbon nanotubes and metallized substrate

Energy Technology Data Exchange (ETDEWEB)

Chen, M X; Gan, Z Y; Liu, S [School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Song, X H, E-mail: chimish@163.com [Division of MOEMS, Wuhan National Lab for Optoelectronics, Wuhan 430074 (China)

2011-08-26

Vertically aligned carbon nanotube (VACNT) turf is proposed for use as an electrical and thermal contact material. For these applications, one route for circumventing the high temperatures required for VACNT growth using chemical vapor deposition (CVD) is used to grow firstly VACNTs on one substrate and then transfer them to other substrates. In this work, a nano thermocompression bonding technique between VACNTs and a metallized substrate is developed to allow dry mechanical transfer of the VACNTs. Unlike the diffusion bonding between two bulk materials, nano metal clusters have a high surface energy and the atoms are very active to form alloy with the contacted bulk metal material even at much lower temperatures, so nano thermocompression bonding can decrease the bonding temperature (150 deg. C) and pressure (1 MPa) and greatly shorten the bonding time from hours to 20 min. A debonding experiment shows that the bonding strength between VACNTs and the metallized layer is so high that a break is less likely to occur at the bonding interface.

Orthodontic bracket bonding to glazed full-contour zirconia

Directory of Open Access Journals (Sweden)

Ji-Young Kwak

2016-05-01

Full Text Available Objectives This study evaluated the effects of different surface conditioning methods on the bond strength of orthodontic brackets to glazed full-zirconia surfaces. Materials and Methods Glazed zirconia (except for the control, Zirkonzahn Prettau disc surfaces were pre-treated: PO (control, polishing; BR, bur roughening; PP, cleaning with a prophy cup and pumice; HF, hydrofluoric acid etching; AA, air abrasion with aluminum oxide; CJ, CoJet-Sand. The surfaces were examined using profilometry, scanning electron microscopy, and electron dispersive spectroscopy. A zirconia primer (Z-Prime Plus, Z or a silane primer (Monobond-S, S was then applied to the surfaces, yielding 7 groups (PO-Z, BR-Z, PP-S, HF-S, AA-S, AA-Z, and CJ-S. Metal bracket-bonded specimens were stored in water for 24 hr at 37℃, and thermocycled for 1,000 cycles. Their bond strengths were measured using the wire loop method (n = 10. Results Except for BR, the surface pre-treatments failed to expose the zirconia substructure. A significant difference in bond strengths was found between AA-Z (4.60 ± 1.08 MPa and all other groups (13.38 ± 2.57 - 15.78 ± 2.39 MPa, p < 0.05. For AA-Z, most of the adhesive remained on the bracket. Conclusions For bracket bonding to glazed zirconia, a simple application of silane to the cleaned surface is recommended. A zirconia primer should be used only when the zirconia substructure is definitely exposed.

Effect of Sodium Ascorbate and Delayed Bonding on the Bond Strength of Silorane and Two-step Self-etch Adhesive Systems in Bleached Enamel

Directory of Open Access Journals (Sweden)

Mehdi Abed Kahnemooyi

2014-12-01

Full Text Available Background and aims. Studies have shown decreased bond strength of composite resin to human and bovine bleached enamel. This study evaluated the effect of sodium ascorbate and delayed bonding on the bond strength of two adhesive systems to bleached enamel. Materials and methods. The labial surfaces of 150 sound bovine incisor teeth were abraded with abrasive paper. The teeth were randomly divided into 8 groups: A: control; B: bleached with 35% hydrogen peroxide; C: bleached with 35% hydrogen peroxide + sodium ascorbate gel; and D: bleached with 35% hydrogen peroxide + delayed bonding. In groups A‒D, silorane adhesive system and Filtek silorane composite resin were used. In groups E‒H, the same preparation methods of groups A‒D were used. Two-step self-etch Clearfil SE Bond adhesive systems and AP-X composite resin were administered. Shear bond strength of each group was measured. Two samples were prepared for each surface preparation for ultrastructural evaluation. Two-way ANOVA and Tukey test were used for data analysis at P<0.05. Results. The interaction between the adhesive system type and surface preparation protocol was significant (P=0.014, with significant differences in shear bond strengths in terms of the adhesive systems (P<0.01. There were significant differences in shear bond strength in terms of surface preparation techniques irrespective of the adhesive system (P<0.01. Conclusion. The results showed that bleaching with 35% hydrogen peroxide decreased the shear bond strength values with both adhesive systems, and a one-week delay in bonding and 10% sodium ascorbate for 10 minutes restored the bond strength in both adhesive systems.

Bonding and vibrational dynamics of a large π-conjugated molecule on a metal surface

International Nuclear Information System (INIS)

Temirov, R; Soubatch, S; Lassise, A; Tautz, F S

2008-01-01

The interplay between the substrate bonding of a large π-conjugated semiconductor molecule and the dynamical properties of the metal-organic interface is studied, employing the prototypical PTCDA/Ag(111) monolayer as an example. Both the coupling of molecular vibrations to the electron-hole-pair continuum of the metal surface and the inelastic scattering of tunnelling electrons by the molecular vibrations on their passage through the molecule are considered. The results of both types of experiment are consistent with the findings of measurements which probe the geometric and electronic structure of the adsorbate-substrate complex directly; generally speaking, they can be understood in the framework of standard theories for the electron-vibron coupling. While the experiments reported here in fact provide additional qualitative insights into the substrate bonding of our π-conjugated model molecule, their detailed quantitative understanding would require a full calculation of the dynamical interface properties, which is currently not available

Physical mechanisms of copper-copper wafer bonding

International Nuclear Information System (INIS)

Rebhan, B.; Hingerl, K.

2015-01-01

The study of the physical mechanisms driving Cu-Cu wafer bonding allowed for reducing the bonding temperatures below 200 °C. Metal thermo-compression Cu-Cu wafer bonding results obtained at such low temperatures are very encouraging and suggest that the process is possible even at room temperature if some boundary conditions are fulfilled. Sputtered (PVD) and electroplated Cu thin layers were investigated, and the analysis of both metallization techniques demonstrated the importance of decreasing Cu surface roughness. For an equal surface roughness, the bonding temperature of PVD Cu wafers could be even further reduced due to the favorable microstructure. Their smaller grain size enhances the length of the grain boundaries (observed on the surface prior bonding), acting as efficient mass transfer channels across the interface, and hence the grains are able to grow over the initial bonding interface. Due to the higher concentration of random high-angle grain boundaries, this effect is intensified. The model presented is explaining the microstructural changes based on atomic migration, taking into account that the reduction of the grain boundary area is the major driving force to reduce the Gibbs free energy, and predicts the subsequent microstructure evolution (grain growth) during thermal annealing

Improved adhesion of Ag NPs to the polyethylene terephthalate surface via atmospheric plasma treatment and surface functionalization

Science.gov (United States)

Shen, Tao; Liu, Yong; Zhu, Yan; Yang, De-Quan; Sacher, Edward

2017-07-01

Ag nanoparticles (NPs) have been widely applied, as important antibacterial materials, on textile and polymer surfaces. However, their adhesion to nonreactive polymer surfaces is generally too weak for many applications. Here, we propose a two-step process, atmospheric plasma treatment followed by a surface chemical modification process, which enhances their adhesion to polyethylene terephthalate (PET) surfaces. We found that, compared to either plasma treatments or surface chemical functionalizations, alone, this combination greatly enhanced their adhesion. The plasma treatment resulted in an increase of active sites (sbnd OH, sbnd CHdbnd O and COOH) at the PET surface, permitting increased bonding to 3-aminopropyltriethoxysilane (APTES), whose sbnd NH2 groups were then able to form a bonding complex with the Ag NPs.

Influence of surface conditions and silane agent on the bond of resin to IPS Empress 2 ceramic.

Science.gov (United States)

Spohr, Ana Maria; Sobrinho, Lourenço Correr; Consani, Simonides; Sinhoreti, Mario Alexandre Coelho; Knowles, Jonathan C

2003-01-01

The aim of this study was to evaluate the effect of different ceramic surface treatments on the tensile bond strength between IPS Empress 2 ceramic framework and Rely X adhesive resin cement, with or without the application of a silane coupling agent. One hundred twenty disks were made, embedded in resin, and randomly divided into six groups: group 1 = sandblasting (100 microm), no silanation; group 2 = sandblasting (100 microm), silane treatment; group 3 = sandblasting (50 microm), no silanation; group 4 = sandblasting (50 microm), silane treatment; group 5 = hydrofluoric acid etching, no silanation; and group 6 = hydrofluoric acid etching, silane treatment. The disks were bonded into pairs with adhesive resin cement. All samples were stored in distilled water at 37 degrees C for 24 hours and then thermocycled. The samples were submitted to tensile testing. The use of silane improved the bond strength in relation to the groups in which silane was not applied (P Empress 2 ceramic framework and resin agent.

30 CFR 800.30 - Replacement of bonds.

Science.gov (United States)

2010-07-01

... 30 Mineral Resources 3 2010-07-01 2010-07-01 false Replacement of bonds. 800.30 Section 800.30... REQUIREMENTS FOR SURFACE COAL MINING AND RECLAMATION OPERATIONS UNDER REGULATORY PROGRAMS § 800.30 Replacement... replacement performance bonds. Replacement of a performance bond pursuant to this section shall not constitute...

Method to improve commercial bonded SOI material

Science.gov (United States)

Maris, Humphrey John; Sadana, Devendra Kumar

2000-07-11

A method of improving the bonding characteristics of a previously bonded silicon on insulator (SOI) structure is provided. The improvement in the bonding characteristics is achieved in the present invention by, optionally, forming an oxide cap layer on the silicon surface of the bonded SOI structure and then annealing either the uncapped or oxide capped structure in a slightly oxidizing ambient at temperatures greater than 1200.degree. C. Also provided herein is a method for detecting the bonding characteristics of previously bonded SOI structures. According to this aspect of the present invention, a pico-second laser pulse technique is employed to determine the bonding imperfections of previously bonded SOI structures.

A classical trajectory study of the adatom -surface bond dissociation in the collision reaction between an adsorbed H atom and an N2 molecule

International Nuclear Information System (INIS)

Bayhan, U.

2005-01-01

The collisionnal dissociation of the Adatom-Surface bond in the diatomic molecule N2(gas)/H(ads) collision taking place on a W(100) bcc-structure surface have been studied by classical trajectory method over the collision energy ranges (0.1-2.0 eV ) and the attractive well depth (0.19-4.0 eV). of the N2 molecule (gas)/H(ads) interactions. When the energy accumulate into the adatom bond, thus leading to a a large dissociation probability

TOPICAL REVIEW Progress in cold roll bonding of metals

Directory of Open Access Journals (Sweden)

Long Li, Kotobu Nagai and Fuxing Yin

2008-01-01

Full Text Available Layered composite materials have become an increasingly interesting topic in industrial development. Cold roll bonding (CRB, as a solid phase method of bonding same or different metals by rolling at room temperature, has been widely used in manufacturing large layered composite sheets and foils. In this paper, we provide a brief overview of a technology using layered composite materials produced by CRB and discuss the suitability of this technology in the fabrication of layered composite materials. The effects of process parameters on bonding, mainly including process and surface preparation conditions, have been analyzed. Bonding between two sheets can be realized when deformation reduction reaches a threshold value. However, it is essential to remove surface contamination layers to produce a satisfactory bond in CRB. It has been suggested that the degreasing and then scratch brushing of surfaces create a strong bonding between the layers. Bonding mechanisms, in which the film theory is expressed as the major mechanism in CRB, as well as bonding theoretical models, have also been reviewed. It has also been showed that it is easy for fcc structure metals to bond compared with bcc and hcp structure metals. In addition, hardness on bonding same metals plays an important part in CRB. Applications of composites produced by CRB in industrial fields are briefly reviewed and possible developments of CRB in the future are also described.

Effect of surface treatments on the bond strength between resin cement and differently sintered zirconium-oxide ceramics.

Science.gov (United States)

Yenisey, Murat; Dede, Doğu Ömür; Rona, Nergiz

2016-01-01

This study investigated the effects of surface treatments on bond strength between resin cement and differently sintered zirconium-oxide ceramics. 220 zirconium-oxide ceramic (Ceramill ZI) specimens were prepared, sintered in two different period (Short=Ss, Long=Ls) and divided into ten treatment groups as: GC, no treatment; GSil, silanized (ESPE-Sil); GSilPen, silane flame treatment (Silano-Pen); GSb, sandblasted; GSbSil, sandblasted+silanized; GSbCoSil, sandblasted+silica coated (CoJet)+silanized; GSbRoSil, sandblasted+silica coated (Rocatech-Plus)+silanized; GSbDSil, sandblasted+diamond particle abraded (Micron MDA)+silanized; GSbSilPen, sandblasted+silane flame treatment+silanized; GSbLSil, sandblasted+Er:Yag (Asclepion-MCL30) laser treated+silanized. The composite resin (Filtek Z-250) cylinders were cemented to the treated ceramic surfaces with a resin cement (Panavia F2.0). Shear bond strength test was performed after specimens were stored in water for 24h and thermo-cycled for 6000 cycles (5-55 °C). Data were statistically analyzed with two-way analysis of variance (ANOVA) and Tamhane's multiple comparison test (α=0.05). According to the ANOVA, sintering time, surface treatments and their interaction were statistically significant (pzirconium-oxide ceramics. Copyright © 2015 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

The role of short-range Cys171-Cys178 disulfide bond in maintaining cutinase active site integrity: A molecular dynamics simulation

International Nuclear Information System (INIS)

Matak, Mehdi Youssefi; Moghaddam, Majid Erfani

2009-01-01

Understanding structural determinants in enzyme active site integrity can provide a good knowledge to design efficient novel catalytic machineries. Fusarium solani pisi cutinase with classic triad Ser-His-Asp is a promising enzyme to scrutinize these structural determinants. We performed two MD simulations: one, with the native structure, and the other with the broken Cys171-Cys178 disulfide bond. This disulfide bond stabilizes a turn in active site on which catalytic Asp175 is located. Functionally important H-bonds and atomic fluctuations in catalytic pocket have been changed. We proposed that this disulfide bond within active site can be considered as an important determinant of cutinase active site structural integrity.

Bond strength of the porcelain repair system to all-ceramic copings and porcelain.

Science.gov (United States)

Lee, Sang J; Cheong, Chan Wook; Wright, Robert F; Chang, Brian M

2014-02-01

The purpose of this study was to investigate the shear bond strength of the porcelain repair system on alumina and zirconia core ceramics, comparing this strength with that of veneering porcelain. Veneering ceramic (n = 12), alumina core (n = 24), and zirconia core (n = 24) blocks measuring 10 × 5 × 5 mm(3) were fabricated. Veneering ceramic blocks were used as the control. Alumina and zirconia core blocks were divided into 2 groups (n = 12 each), and a slot (2 × 2 × 4 mm(3)) filled with veneering ceramics was prepared into one of the alumina and zirconia core groups (n = 12). Followed by surface treatments of micro-abrasion with 30 μm alumina particles, etching with 35% phosphoric acid and silane primer and bond, composite resin blocks (2 × 2 × 2 mm(3)) were built up and light polymerized onto the treated surfaces by 3 configurations: (a) composite blocks bonded onto veneering ceramic surface alone, (b) composite blocks bonded onto alumina core or zirconia core surfaces, (c) a 50% surface area of the composite blocks bonded to veneering ceramics and the other 50% surface area of the composite blocks to alumina core or zirconia core surfaces. The shear bond strength of the composite to each specimen was tested by a universal testing machine at a 0.5 mm/min crosshead speed. The shear bond strength was analyzed by unpaired t-tests for within the configuration groups and ANOVA for among the different configuration groups. When the mean shear bond strength was compared within groups of the same configuration, there were no statistically significant differences. Comparison of the shear bond strength among groups of different configurations revealed statistically significant differences. The mean shear bond strength of composite onto 100% veneering ceramic surface and composite onto 50% veneering 50% all-ceramic cores was statistically higher than that of composite onto 100% all-ceramic cores; however, the differences of the shear bond strength of composite bonded

Simplified nonplanar wafer bonding for heterogeneous device integration

Science.gov (United States)

Geske, Jon; Bowers, John E.; Riley, Anton

2004-07-01

We demonstrate a simplified nonplanar wafer bonding technique for heterogeneous device integration. The improved technique can be used to laterally integrate dissimilar semiconductor device structures on a lattice-mismatched substrate. Using the technique, two different InP-based vertical-cavity surface-emitting laser active regions have been integrated onto GaAs without compromising the quality of the photoluminescence. Experimental and numerical simulation results are presented.

Composite Bonding to Stainless Steel Crowns Using a New Universal Bonding and Single-Bottle Systems

OpenAIRE

Mohammad Ali Hattan; Sharat Chandra Pani; Mohammad AlOmari

2013-01-01

Aim. The aim of this study is to evaluate the shear bond strength of nanocomposite to stainless steel crowns using a new universal bonding system. Material and Methods. Eighty (80) stainless steel crowns (SSCs) were divided into four groups (20 each). Packable nanocomposite was bonded to the lingual surface of the crowns in the following methods: Group A without adhesive (control group), Group B using a new universal adhesive system (Scotchbond Universal Adhesive, 3M ESPE, Seefeld, Germany), ...

Microshear Bond Strength of OptiBond All-in-One Self-adhesive Agent to Er:YAG Laser Treated Enamel After Thermocycling and Water Storage.

Science.gov (United States)

Kasraei, Shahin; Yarmohammadi, Ebrahim; Ghazizadeh, Mohammad Vahid

2016-01-01

Introduction: This study aimed to compare the microshear bond strength of composite to enamel treated with Erbium-Doped Yttrium Aluminum Garnet (Er:YAG) laser using a self-etch one step bonding agent. Methods: Seventy-six enamel surfaces were prepared from 38 sound human third molar teeth. Specimens were randomly divided into four groups of 18. The enamel surface in half the specimens was irradiated with Er:YAG laser. One extra specimen from each group was evaluated under a scanning electron microscope (SEM). Composite micro-cylinders were bonded to the specimen surfaces using OptiBond All-In-One (OB) adhesive agent and stored in distilled water for 24 hours. Half the specimens were thermocycled (2000 cycles) and stored in distilled water at 37°C for three months (TW). The microshear bond strength of composite to enamel was measured using a universal testing machine at a crosshead speed of 1 mm/min. The fractured surfaces were evaluated under a stereomicroscope at ×40 magnification to determine the mode of failure. Data were analyzed using repeated measures analysis of variance (ANOVA) and t test. Results: The mean values (±standard deviation) were 17.96 ± 2.92 MPa in OB group, 22.29 ± 4.25 MPa in laser + OB group, 18.11 ± 3.52 MPa in laser + OB + TW group and 9.42 ± 2.47 MPa in OB + TW group. Repeated measures ANOVA showed that laser irradiation increased the microshear bond strength ( P Enamel surface preparation with Er:YAG laser is recommended to enhance the durability of the bond of self-etch bonding systems to enamel.

Non-silicon substrate bonding mediated by poly(dimethylsiloxane) interfacial coating

Science.gov (United States)

Zhang, Hainan; Lee, Nae Yoon

2015-02-01

In this paper, we introduce a simple and robust strategy for bonding poly(dimethylsiloxane) (PDMS) with various thermoplastic substrates to fabricate a thermoplastic-based closed microfluidic device and examine the feasibility of using the proposed method for realizing plastic-plastic bonding. The proposed bonding strategy was realized by first coating amine functionality on an oxidized thermoplastic surface. Next, the amine-functionalized surface was reacted with a monolayer of low-molecular-weight PDMS, terminated with epoxy functionality, by forming a robust amine-epoxy bond. Both the PDMS-coated thermoplastic and PDMS were then oxidized and permanently assembled at 25 °C under a pressure of 0.1 MPa for 15 min, resulting in PDMS-like surfaces on all four inner walls of the microchannel. Surface characterizations were conducted, including water contact angle measurement, X-ray photoelectron spectroscopy (XPS), and fluorescence measurement, to confirm the successful coating of the thin PDMS layer on the plastic surface, and the bond strength was analyzed by conducting a peel test, burst test, and leakage test. Using the proposed method, we could successfully bond various thermoplastics such as poly(methylmethacrylate) (PMMA), polycarbonate (PC), polystyrene (PS), and poly(ethylene terephthalate) (PET) with PDMS without the collapse or deformation of the microchannel, and the proposed method was successfully extended to the bonding of two thermoplastics, PMMA, and PC.

Bonding Effectiveness of Luting Composites to Different CAD/CAM Materials.

Science.gov (United States)

Peumans, Marleen; Valjakova, Emilija Bajraktarova; De Munck, Jan; Mishevska, Cece Bajraktarova; Van Meerbeek, Bart

To evaluate the influence of different surface treatments of six novel CAD/CAM materials on the bonding effectiveness of two luting composites. Six different CAD/CAM materials were tested: four ceramics - Vita Mark II; IPS Empress CAD and IPS e.max CAD; Celtra Duo - one hybrid ceramic, Vita Enamic, and one composite CAD/CAM block, Lava Ultimate. A total of 60 blocks (10 per material) received various mechanical surface treatments: 1. 600-grit SiC paper; 2. sandblasting with 30-μm Al2O3; 3. tribochemical silica coating (CoJet). Subsequent chemical surface treatments involved either no further treatment (control), HF acid etching (HF), silanization (S, or HF acid etching followed by silanization (HF+S). Two specimens with the same surface treatment were bonded together using two dual-curing luting composites: Clearfil Esthetic Cement (self-etching) or Panavia SA Cement (self-adhesive). After 1 week of water storage, the microtensile bond strength of the sectioned microspecimens was measured and the failure mode was evaluated. The bonding performance of the six CAD/CAM materials was significantly influenced by surface treatment (linear mixed models, p CAD (p = 0.0115), and Lava Ultimate (p CAD/CAM materials: Vita Mark II and IPS Empress CAD: S, HF+S; Celtra Duo: HF, HF+S; IPS e.max CAD: HF+S; Vita Enamic: HF+S, S. For Lava Ultimate, the highest bond strengths were obtained with HF, S, HF+S. Failure analysis showed a relation between bond strength and failure type: more mixed failures were observed with higher bond strengths. Mainly adhesive failures were noticed if no further surface treatment was done. The percentage of adhesive failures was higher for CAD/CAM materials with higher flexural strength (Celtra Duo, IPS e.max CAD, and Lava Ultimate). The bond strength of luting composites to novel CAD/CAM materials is influenced by surface treatment. For each luting composite, an adhesive cementation protocol can be specified in order to obtain the highest bond to the

Surface Reconstruction-Induced Coincidence Lattice Formation Between Two-Dimensionally Bonded Materials and a Three-Dimensionally Bonded Substrate

NARCIS (Netherlands)

Boschker, Jos E.; Momand, Jamo; Bragaglia, Valeria; Wang, Ruining; Perumal, Karthick; Giussani, Alessandro; Kooi, Bart J.; Riechert, Henning; Calarco, Raffaella

Sb2Te3 films are used for studying the epitaxial registry between two-dimensionally bonded (2D) materials and three-dimensional bonded (3D) substrates. In contrast to the growth of 3D materials, it is found that the formation of coincidence lattices between Sb2Te3 and Si(111) depends on the geometry

N-Heterocyclic carbenes on close-packed coinage metal surfaces: bis-carbene metal adatom bonding scheme of monolayer films on Au, Ag and Cu.