Substrate Specimens Research Articles

BOND STRENGTH AND INTERFACIAL MORPHOLOGY OF A MULTIMODE ADHESIVE RESIN CEMENT TO ENAMEL AND DENTIN

Introduction: Resin cements are used for cementation of indirect restorations. A high-quality adhesion to tooth structure is primordial for the success of indirect cemented restorations. Objectives: Were to assess the shear bond strength of RelyX ultimate adhesive resin cement to both enamel and dentin when used in different application modes (self-etch and total-etch) and to study resin-tooth interfaces using SEM. Materials and methods: 40 enamel specimens and 40 dentin specimens were used in this study. Each substrate specimens were randomly divided into four groups of 10 specimens each according to resin cement applied: Enamel groups: Group A1: RelyX ultimate as total-etch; Group A2: RelyX ultimate as self-etch; Group A3: Variolink II; Group A4: Multilink automix. Dentin groups: Group B1: RelyX ultimate as total-etch; Group B2: RelyX ultimate as self-etch; Group B3: Variolink II; Group B4: Multilink automix. Resin cements were built over the surfaces following manufacturer's instructions in a plastic tube. All specimens were thermocycled (500 cycles, 5°/55°C, 15 sec dwell time) then shear bond strength was measured in MPa and data were analyzed using F-test (ANOVA) and Post Hoc test. Three specimens from each group were further sectioned, gold sputtered and evaluated under SEM. Results: All enamel groups showed a statistically significant difference for shear bond strength with P <0.001. Group A1 revealed the highest mean value of 35.60 MPa. While for dentin, there was no statistically significant differences among groups with P=0.053. Interfacial morphology of RelyX ultimate in total-etch mode showed better interface morphology and improved tag length compared to respective self-etch counterpart. Conclusions: An etching step prior to multi-mode adhesive resin cement increased its bond strength values and improved its penetration pattern to both enamel and dentin, also length of resin tags formed by total-etch adhesives seems not to play an important role in determining bond strength. Keywords: Resin cements, Adhesives, Multi-mode, dental substrates, bonding, interface.

Fatigue and fracture behavior of laser clad repair of AerMet® 100 ultra-high strength steel

The effect of laser cladding on the fatigue and fracture behavior under variable amplitude loading is a major consideration for the development of laser cladding process to repair high value complex fatigue critical aerospace military components, that otherwise would be replaced. The selected material, AerMet®100, is a widely used ultra-high strength steel in current and next generation aerospace components, such as landing gears. Laser cladding was performed using AerMet® 100 powder on AerMet® 100 fatigue substrate specimens. No micro-cracking and very little porosity were observed in the clad layer. The fatigue tests were performed under variable amplitude loading with a maximum stress of 1000MPa. Residual stress, microstructure, and hardness, was also evaluated. Both the as-clad and post-heat treated (PHT) samples were compared to a baseline sample with an artificial notch to simulate damaged condition. Results show that laser cladding significantly improves fatigue life, as compared to the baseline sample with a notch. However, the fatigue life of the as-clad sample is lower as compared to a baseline sample without a notch. A compressive residual stress of 300–500MPa was observed in the clad region and HAZ. The fracture modes in the as-clad specimen consisted mainly of tearing topology surface and some regions of decohesive rupture through the columnar austenite grains. The PHT condition however was not effective in improving the fatigue life. The fracture modes showed mainly decohesive rupture, and as a consequence, reduced the fatigue life.

Repair bond strength of dual-cured resin composite core buildup materials

The reparability of dual-cured resin composite core buildup materials using a light-cured one following one week or three months storage, prior to repair was evaluated. Two different dual-cured resin composites; Cosmecore™ DC automix and Clearfil™ DC automix core buildup materials and a light-cured nanofilled resin composite; Filtek™ Z350 XT were used. Substrate specimens were prepared (n=12/each substrate material) and stored in artificial saliva at 37°C either for one week or three months. Afterward, all specimens were ground flat, etched using Scotchbond™ phosphoric acid etchant and received Single Bond Universal adhesive system according to the manufacturers’ instructions. The light-cured nanofilled resin composite (Filtek™ Z350 XT) was used as a repair material buildup. To determine the cohesive strength of each solid substrate material, additional specimens from each core material (n=12) were prepared and stored for the same periods. Five sticks (0.8±0.01mm2) were obtained from each specimen (30 sticks/group) for microtensile bond strength (μTBS) testing. Modes of failure were also determined. Two-way ANOVA revealed a significant effect for the core materials but not for the storage periods or their interaction. After one week, dual-cured resin composite core buildup materials (Cosmecore™ DC and Clearfil™ DC) achieved significantly higher repair μTBS than the light-cured nanofilled resin composite (Filtek™ Z350 XT). However, Clearfil™ DC revealed the highest value, then Cosmecore™ DC and Filtek™ Z350 XT, following storage for 3-month. Repair strength values recovered 64–86% of the cohesive strengths of solid substrate materials. The predominant mode of failure was the mixed type. Dual-cured resin composite core buildup materials revealed acceptable repair bond strength values even after 3-month storage.

Warpage Analysis of Electroplated Cu Films on Fiber-Reinforced Polymer Packaging Substrates

This paper presents a warpage analysis method that predicts the warpage behavior of electroplated Cu films on glass fiber-reinforced polymer (GFRP) packaging substrates. The analysis method is performed using the following sequence: fabricate specimens for scanning 3D contours, transform 3D data into curvatures, compute the built-in stress of the film using a stress-curvature analytic model, and verify it through comparisons of the finite element method (FEM) simulations with the measured data. The curvature is used to describe the deflection and warpage modes and orientations of the specimen. Two primary factors that affect the warpage behavior of the electroplated Cu film on FRP substrate specimens are investigated. The first factor is the built-in stress in a Cu film that explains the room temperature warpage of the specimen under no thermal process. The second factor is the misfit of the coefficient of thermal expansion (CTE) between the Cu and FRP layer, which is a dominant factor during the temperature change. The calculated residual stress, and predicted curvatures using FEM simulation throughout the reflow process temperature range between 25 and 180 °C are proven to be accurate by the comparison of the FEM simulations and experiment measurements.

Repair Bond Strength of Aged Silorane-based Composite Using Intermediate Adhesive Systems Based on Different Monomers.

To investigate the effect of pre-repair aging periods and intermediate adhesive systems based on different monomers on the repair bond strength of silorane-based resin composite. A total of 32 Filtek P90 (3M ESPE) substrate specimens (4 mm diameter and 4 mm height) were made. Substrate specimens were grouped according to the pre-repair time periods into four groups (n = 8/group): 15 to 30 min, 24 h, 1 month, and 3 months. All substrate specimens were ground flat using a diamond stone and were etched using Scotchbond phosphoric acid etchant (3M ESPE). The specimens of each pre-repair time period were equally distributed among the two repair groups, using either silorane-based (P90 System Adhesive) or acrylamide-based (AdheSE One F, Ivoclar Vivadent) intermediate adhesive systems. Specimens of P90 System adhesive received Filtek P90 as the repair resin composite, and Tetric N-Ceram (Ivoclar Vivadent) was used with AdheSE One F specimens. Additional specimens were made from the repair resin composite materials to study the cohesive strength. Specimens were sliced into sticks (0.6 ± 0.01 mm2) for microtensile bond strength testing (μTBS). Modes of failure were determined. Two-way ANOVA with repeated measures revealed no significant effect for the pre-repair aging periods, intermediate adhesive systems based on different monomers, or their interaction on repair bond strength of silorane-based resin composite. Up to 3 months of pre-aging the repaired silorane-based resin composite had no negative effect on its repair bond strength, even when an intermediate adhesive system based on a different monomer (acrylamide) was used.

Hot corrosion behavior of a centimeter Fe-based amorphous composite coating prepared by laser cladding in molten Na2SO4 + K2SO4 salts

An Fe-based amorphous composite coating with a thickness of 15mm was prepared by laser cladding method. Hot corrosion behavior of the composite coating in the molten Na2SO4+K2SO4 at 650°C was investigated by the weight change kinetics, X-ray diffraction (XRD), scanning electron microscopy (SEM) as well as energy dispersive X-ray spectroscopy (EDS). The mass gain measurements were performed after each cycle to establish the kinetics of corrosion using the thermogravimetric technique. The coating consisted of an Fe–Cr-rich amorphous matrix and several kinds of borides. Compared to the microstructure of the substrate specimens, no spallation or crack of the oxide scales was observed on the coating surface, indicating that the thermal stresses on the composite coating are lower than the substrate specimens. The results indicated that the composite coating exhibited high hot corrosion resistance in the molten Na2SO4+K2SO4 due to the amorphous composite microstructure, which is in favor of the formation of a continuous and protective Cr2O3 oxide scale. Usually, the Cr2O3 oxide scale acts as an effective barrier to the inward diffusion of corrosive species during the hot corrosion process.

Isothermal solidification stage during transient liquid-phase bonding single-crystal superalloys

In this work, the isothermal solidification stage during transient liquid-phase bonding (TLP) single-crystal superalloys has been investigated. Experiments were performed to ascertain the bonding microstructures and the kinetics during the isothermal solidification. The results have shown that the isothermal solidification stage deviates from the standard parabolic TLP models. Lots of the borides with fine, short bar and acicular morphologies formed in the diffusion affected zone (DAZ) in the thick wall and thin wall substrate specimens at the isothermal solidification stage. Electron probe microanalysis results have shown that there exists B composition peak in the DAZ. Examination of the bonding kinetics presented that there are three stages in the isothermal solidification stage: initial stage, transient stage and final stage with different growth velocity of the isothermal solidification zone (ISZ). And the relationship of the width of the ISZ with the square root of the bonding time didn’t satisfy the parabolic relationship. Based on the microstructures and kinetics observed, a film ISZ mechanism is proposed, and a model is constructed to illustrate the isothermal solidification stage during bonding single-crystal superalloys.

Wear behavior between zirconia and titanium as an antagonist on fixed dental prostheses

The aim of this in vitro study was to investigate the wear behavior of the abrader when tetragonal zirconia polycrystal (TZP), cp-titanium (CpTi) and Ti–6Al–4V alloy (TiAlV) were used as the antagonist on fixed dental prostheses (FDPs). Both hemisphere abrader and flat substrate specimens were prepared using TZP, CpTi and TiAlV. Two-body wear tests were performed in distilled water, and the wear volume of the abrader specimen was measured to evaluate the wear behavior. In addition, scanning microscopic observation and an electron probe micro-analysis were performed to elucidate the underlying mechanism of the wear. The wear volume of CpTi and TiAlV abrader specimens was approximately 20 times larger than that of TZP abrader specimen against all substrate specimens. This is due to the differences in hardness between the ultra-hardness of TZP and the comparatively low hardness of CpTi and TiAlV. The wear volume of CpTi and TiAlV abrader specimens against the TZP substrate was significantly smaller than for the CpTi and TiAlV substrates despite the hardness of TZP being much larger than those of CpTi and TiAlV. This phenomenon may be based on the adhesive wear mechanism. Elements of Ti, Al and V originating in the TiAlV substrate were detected adhering to the abrader CpTi specimen. These results suggest that FDPs of CpTi and TiAlV are susceptible to wear against not only TZP but also CpTi and TiAlV in contrast to TZP FDPs.

Wear performance of bovine tooth enamel against translucent tetragonal zirconia polycrystals after different surface treatments.

The wear performances of bovine tooth enamel (BTE) against translucent tetragonal zirconia polycrystals (TZP) compared to that of feldspar porcelain and the influence of surface treatments of translucent TZP were investigated by the two-body wear test. Translucent TZP and feldspar porcelain were used as hemisphere abrader specimens with a radius of curvature of 5 mm; flat BTE surfaces were used as substrate specimens. The cross-sectional area of the worn surfaces of the substrates and the wear volume of the antagonist abraders were measured. Surface roughness, hardness and coefficient of friction as well as SEM observations and EPMA analyses were also performed to investigate the underlying mechanism of wear. The results suggested that BTE is less susceptible to wear when translucent TZP is used as the antagonist in contrast to the use of feldspar porcelain, and that surface treatment of the TZP abraders significantly influenced the wear of BTE substrates.

Long Term Water Storage Deteriorates Bonding of Composite Resin to Alumina and Zirconia Short Communication

Objective of this study was to evaluate the effects of long term water storage and ageing on the bond strength of resin composite cement to yttria-stabilized zirconium dioxide (zirconia) and dialuminium trioxide (alumina). Substrate specimens of alumina and zirconia were air particle abraded with dialuminium trioxide before priming and application of composite resin. Priming was made with gamma metharyloxy-trimethoxysilane or acryloxypropyl-trimethoxysilane monomer after which the intermediate dimethacrylate resin was applied and photopolymerized. This was followed by curing particulate composite resin cement (Relyx ARC) to the substrate as a resin stub. The ageing methods of the specimens (n=6) were: (1) they stored four years in 37±1ºC distilled water, (2) thermocycled 8000 times between 55±1ºC and 5±1ºC, (3) stored first in water for four years and then thermocycled. Specimens which were stored dry, were used as controls. Bonding of composite resin was measured by shear-bond strength test set-up. Both thermocycling and long-term water storage decreased significantly shear bond strength values compared to the control group (from the level of 20 MPa to 5 MPa) regardless of the used primer or the type of the substrate. Combination of four years water storage and thermocyling reduced the bond strength even more, to the level of two to three megapascals. In can be concluded that water storage and thermocycling itselves, and especially combination of water storage and thermocycling can cause considerable reduction in the bond strength of composite resin cement to alumina and zirconia.

RETRACTED: The Adhesion Properties of Parylene-C Thin Films

Retracted article: This work aims to enhance the adhesion of Parylene-C (poly-chloro-p-xylylene C) thin film on PMMA, Glass and Aluminum substrates by chemical vapor deposition, surface improvement and treatment of substrate as well as analysis of film on Glass, PMMA, Aluminum and its surface adhesion by dipping under A-174 silane solution and conducting on plasma treatment (18 W). The results show that: (1) After oxygen-plasma pretreatment, the surface roughness of the 200nm-thickness film on glass substrate specimens decreases from 18nm to 7nm. (2) After dipped in prescription solution pretreatment, the residual stress reduces from 107MPa to 64MPa on glass substrate specimens. (3) The critical load of 600nm-thickness film increases from 14.1 to 18.5mN, showing the substrate after dipped in prescription solution pretreatment can improve the adhesion of the Parylene-C thin film on flat glass substrate specimens.

A comparative study on gray and nodular cast irons surface melted by plasma beam

In this study, gray cast iron (GCI) and nodular cast iron (NCI) were surface melted by plasma beam to remove the negative effect of the near-surface graphite phases. Afterward, the modified surfaces were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicated that the molten surface had no pores and cracks, composing of inter-dendrites and eutectics with a hyper-eutectic structure. The cross section micro-hardness as well as the depth of the molten surface was measured. Cementite, martensite, and retained austenite co-existed in the molten surface, improving the micro-hardness from about 315 HV0.1 of the substrate specimens to an average of 1004 HV0.1 and 933 HV0.1 of the molten surface on GCI and NCI specimens treated at the main arc current 55 ± 0.5 A, respectively. Generally, the depth of molten surface on the treated NCI specimen was deeper than that on the treated GCI specimen under the same plasma parameters. Besides, the molten surface on the treated NCI specimen had lower mean surface roughness (Ra) under the same plasma parameters owing to the different graphite shape in cast irons. At the main arc current 55 ± 0.5 A, the mean surface roughness of the treated GCI was 153 ± 5 μm, while that of the treated NCI was 83 ± 4 μm.

Effect of substrate surface roughening and cold spray coating on the fatigue life of AA2024 specimens

The effects of cold spray coating and substrate surface preparation on crack initiation under cyclic loading have been studied on Al2024 alloy specimens. Commercially pure (CP) aluminum feedstock powder has been deposited on Al2024-T351 samples using a cold-spray coating technique known as high velocity particle consolidation. Substrate specimens were prepared by surface grit blasting or shot peening prior to coating. The fatigue behavior of both coated and uncoated specimens was then tested under rotating bend conditions at two stress levels, 180MPa and 210MPa. Scanning electron microscopy was used to analyze failure surfaces and identify failure mechanisms. The results indicate that the fatigue strength was significantly improved on average, up to 50% at 180MPa and up to 38% at 210MPa, by the deposition of the cold-sprayed CP-Al coatings. Coated specimens first prepared by glass bead grit blasting experienced the largest average increase in fatigue life over bare specimens. The results display a strong dependency of the fatigue strength on the surface preparation and cold spray parameters.

Effect of anodizing treatment on the very high cycle fatigue behavior of 2A12-T4 aluminum alloy

The effects of chromic acid anodizing (CAA) and sulfuric acid anodizing (SAA) treatments on the very high cycle fatigue behavior of 2A12-T4 aluminum alloy were investigated through ultrasonic fatigue tests. The results showed that CAA and SAA treatments resulted in an appreciable reduction in the fatigue strength and crack initiation from the interface between the anodizing film and substrate, whereas the fatigue crack of substrate specimens initiated from the specimen subsurface over 5×108cycles. The decrease in fatigue strength of the CAA specimens was associated with the residual tensile stress arising from the elastic mismatch between the anodizing film and the substrate. The defects in SAA film, such as segmentation cracks and overgrowth of the anodizing film into the substrate, contributed to the reduction of fatigue strength and multi-crack initiations. The predicted fatigue limit for SAA specimens well agreed with the experimental results.

Properties of oxide coating on the surface of ZrH1.8 prepared by microarc oxidation with different positive voltages

Zirconia coatings as hydrogen permeation barriers were formed on disk-type ZrH1.8 substrate specimens in phosphate solution system by microarc oxidation technique. Influence of positive voltage on hydrogen permeation barriers on the surface of zirconium hydride was investigated as the main factor. The thickness of total oxide layer increased from 42.5 to 55.0 μm the increase of positive voltage increasing from 325 up to 425 V. The permeation reduction factor (PRF) was observed under different voltages, which increased with the increasing positive voltages. The phase structure of oxide layer was monoclinic ZrO2 and tetragonal ZrO1.88. No reduction reaction occured in the process of hydrogen escaping, and it indicates that hydrogen permeation through oxide layer is restricted.

Measurements of Piezoelectric Coefficient d33 of Lead Zirconate Titanate Thin Films Using a Mini Force Hammer

Lead zirconate titanate (PbZrxTi1-xO3, or PZT) is a piezoelectric material widely used as sensors and actuators. For microactuators, PZT often appears in the form of thin films to maintain proper aspect ratios. One major challenge encountered is accurate measurement of piezoelectric coefficients of PZT thin films. In this paper, we present a simple, low-cost, and effective method to measure piezoelectric coefficient d33 of PZT thin films through use of basic principles in mechanics of vibration. A small impact hammer with a tiny tip acts perpendicularly to the PZT thin-film surface to generate an impulsive force. In the meantime, a load cell at the hammer tip measures the impulsive force and a charge amplifier measures the responding charge of the PZT thin film. Then the piezoelectric coefficient d33 is obtained from the measured force and charge based on piezoelectricity and a finite element modeling. We also conduct a thorough parametric study to understand the sensitivity of this method on various parameters, such as substrate material, boundary conditions, specimen size, specimen thickness, thickness ratio, and PZT thin-film material. Two rounds of experiments are conducted to demonstrate the feasibility and accuracy of this new method. The first experiment is to measure d33 of a PZT disk resonator whose d33 is known. Experimental results show that d33 measured via this method is as accurate as that from the manufacturer's specifications within its tolerance. The second experiment is to measure d33 of PZT thin films deposited on silicon substrates. With the measured d33, we predict the displacement of PZT thin-film membrane microactuators. In the meantime, the actuator displacement is measured via a laser Doppler vibrometer. The predicted and measured displacements agree very well validating the accuracy of this new method.

RETRACTED: Study of Parylene-C Thin Film Deposited on Flat Substrates

Retractes article: This work aims to enhance the surface wettability and adhesion of Parylene-C (poly-chloro-p-xylylene C) thin film on PMMA, glass and aluminum substrates by chemical vapor deposition. The results show that: (1) 0.56, 1, and 1.55g Parylene-C powders can deposit 200, 400, and 600nm films, respectively. (2) After oxygen-plasma pretreatment, the surface roughness of the 200nm-thickness film on glass substrate specimens decreases from 18nm to 7nm. (3) After dipped in prescription solution pretreatment, the residual stress reduces from 107MPa to 64MPa on glass substrate specimens. (4) In contact angle tests, the 600nm-thickness film on various flat substrates deposited process that has surface hydrophobic. (5) The critical load of 600nm-thickness film increases from 14.1 to 18.5mN, showing the substrate after dipped in prescription solution pretreatment can improve the adhesion of the Parylene-C thin film on flat glass substrate specimens.

Two-Year Interfacial Bond Durability and Nanoleakage of Repaired Silorane-Based Resin Composite

To investigate the effect of silane primer application, intermediate adhesive agent/repair composite, and storage period on the interfacial microtensile bond strength (μTBS) of repaired silorane-based resin composite compared with unrepaired composites and on the nanoleakage. Forty-eight 1-month-old substrate specimens from Filtek P90 were roughened, etched, and distributed over two groups (n=24) based on receiving silane (Clearfil Ceramic Primer) or not. Then, half of the specimens (n=12) were repaired with P90 System Adhesive/Filtek P90 and the other half with Adper Scotchbond Multipurpose adhesive/Filtek Z250 resin composite. Within each repair category, repaired specimens were stored in artificial saliva at 37°C for either 24 hours (n=6) or two years before being serially sectioned into sticks (0.6 ± 0.01 mm(2)). From each specimen, two sticks were prepared for nanoleakage determination and four sticks were used for μTBS testing. Additional unrepaired specimens from each composite (n=12) were made to determine the cohesive strength at 24 hours and two years. Mean μTBS were calculated and statistically analyzed. Modes of failure were also determined. General linear model analysis revealed no significant effect for the silane priming, intermediate adhesive agent/repair composite, and storage period or for their interactions on the μTBS values of the repaired specimens. There was no significant difference between the cohesive strength of Filtek P90 and Filtek Z250; both were significantly higher than all repaired categories. At 24 hours, nanoleakage was not detected when silorane-based composite was repaired with the same material. However, after two years, all repair categories showed nanoleakage. Silane application has no effect on μTBS and nanoleakage. Durability of the interfacial bond of repaired silorane-based resin composite appeared successful regardless of the chemistry of the intermediate adhesive agent/composite used for repair. However, nanoleakage was detected early when a different repair intermediate adhesive agent/composite was used.

Laser cladding of Cu0.5NiAlCoCrFeSi high entropy alloy on AZ91D magnesium substrates for improving wear and corrosion resistance

To improve the wear and corrosion properties of AZ91D magnesium alloy, a Cu0.5NiAlCoCrFeSi high entropy alloy (HEA) was fabricated on AZ91D magnesium substrate specimens by laser cladding using elemental powders. The laser-clad coating consists of a fine dendritic structure of a simple BBC phase with nano-size precipitates. The hardness of the coating was some ten times higher than that of the AZ91D substrate and was even higher than that of the same HEA produced by arc melting. The laser-clad coating exhibited good wear resistance, with a wear rate five times lower than that of the substrate material in dry friction wear conditions. The main wear mechanisms of the substrate and the HEA coating were different, the former dominated by both abrasive wear and adhesive wear and the latter by oxidative abrasive wear. With regard to corrosion properties, the laser-clad coating exhibited a more positive corrosion potential and a lower corrosion current density than those of the uncoated substrate material.

Determination of Residual Stress of Hard Film/Soft Substrate Specimens via Unloading Results of Nanoindentation Tests

A method used to determine the residual stress in a hard film deposited on a soft substrate via the unloading load-depth curves was proposed. The unloading curves with transitional behaviors were used to determine the film deflection stiffness, and then the residual stresses were obtained. Significant extra stresses were induced by a cube corner indenter at large depth. In contrast, the indentation-induced stresses could be neglected in cases of Berkovich indentation at relatively small depths.