Absence Of Voids Research Articles

Production of Al-Cu multi-material billet from machining chips using friction stir consolidation (FSC)

This research investigates the production of Al-Cu multi-material billets through a recycling and welding approach. The method employed is the so-called friction stir consolidation (FSE), which involves the consolidation of machining chips by using a tool rotating at specific speed and feed rate. The microstructure and chemical composition of the resulting components are examined using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. The findings indicate that this technique allows producing multi-material billets directly from machining chips with a solid structure and absence of voids.

Application of clustering algorithms to void recognition by 3D ground penetrating radar

The manual interpretation of ground-penetrating radar images is characterised by long interpretation cycles and high staff requirements. The automated interpretation schemes based on support vector machines, digital images, convolutional neural networks and other techniques proposed in recent years mainly detect features from B-scan slices of 3D ground-penetrating radar data, without taking full advantage of the multi-channel acquisition of data from 3D ground-penetrating radar and joint discrimination. This paper proposes a void recognition algorithm based on cluster analysis algorithm, using VRADI algorithm to process 3D ground-penetrating radar B-Scan, using DBSCAN clustering algorithm to divide clusters and remove noise; proposes correlation weighting coefficient Wi,j to quantitatively evaluate the degree of correlation of different survey channels, proposes prime relative position coefficient Pd indicator to quantitatively evaluate the position similarity, and proposes weighted homocentric overlap coefficient Pr indicator to quantify signal similarity. This paper applies the algorithm to carry out physical engineering experiments and uses binary logistic regression analysis to develop a correlation model. The experimental results show that significance of Pd and Pr are less than 0.05, both of which are important influencing indicators for the determination of the presence or absence of void. With an optimal critical probability of 0.4, the recognition accuracy of VRADI algorithm increases from 71.7% to 92.2%. The VRADI algorithm combined with the cluster analysis algorithm outperforms manual recognition in terms of accuracy (92.2% > 83.9%) and recall (90.5% > 86.9%), and the algorithm has good engineering application value.

Effect of powder size in microwave joining of oxygen-free copper to SS304

This paper investigates the prospect of microwave hybrid heating to join oxygen-free copper with stainless steel (SS304). The effect of size of copper (Cu) powder interlayer in the microstructure and mechanical properties of the joint formed is investigated, along with the incites on the mechanism of joint formation. Cu powder of average sizes 4 and 45 μm was studied. The microwave heating rate was observed to be high for 4 μm Cu in the absence of voids or porosities in the joint region. Voids were observed in the interlayer when 45 μm Cu powder was used. The joint was formed due to volumetric diffusion of the major elements of the substrates, e.g. Fe, Cu, Cr that was verified by energy dispersive spectroscopy. Oxides were present for 45 μm Cu which was absent for 4 μm Cu. X-ray diffraction and energy-dispersive X-ray spectroscopy analysis concluded that no intermetallic compound was formed along the interlayer. The micro-hardness of ∼128 HV was observed to be uniform across the interlayer depicting a good metallurgical joint. The maximum tensile shear strength of 83.12 MPa was recorded for 4 μm copper powder and microwave time of 14 min, exhibiting ductile failure of the joint.

Rayleigh-like waves in multilayered elastic media containing voids: Use of the Haskell matrix method

Using the Haskell matrix method, the dispersion relation of Rayleigh-like surface waves propagating through a multilayered elastic solid half-space is derived. Each layer as well as the half-space is assumed to have voids (pores) distributed evenly throughout. This dispersion relation is then reduced for a 2-layered model (single layer over a half-space) to study the characteristics of phase speed of Rayleigh-like wave. For a particular model, the numerical computations are performed to observe the effect of voids on the fundamental mode of Rayleigh-like waves for n = 2 and 3. For the 2-layered model, it is also shown that the particle motion remains elliptical but influenced by the presence of voids. In the absence of voids from the model, the dispersion relation earlier obtained by Haskell (1953) for the case n = 2 is recovered successfully.

Assessment of Four Obturation Methods in Deciduous Teeth Using Digital Radiography: An In Vivo Study.

Aim and objectiveThis study was carried out to comparatively assess the efficiency of four methods of obturation viz Lentulo spiral, Navi tip syringe, Bi directional spiral, and Past inject carrier in deciduous teeth using vista scan.Materials and methodsA total sample of 100 primary root canals [4 groups of 25 canals each] with 2/3rd of root length were selected and randomly allocated into four different obturating techniques, i.e., Group I: Lentulo spiral, Group II: Navi tip syringe, Group III: Bi directional spiral, and Group IV: Past inject carrier. The quality of obturation [Coll and sadrain, 1996] and presence or absence of voids were evaluated by using Vista scan. The recorded data was statistically analyzed.ResultsThe highest mean rank value of optimally filled canals was obtained by Group IV [58.00] followed by Group I [50.00] with no significant difference. The highest mean rank value of under filled canals and over filled canals were obtained by Group III and Group II, respectively, and these results were statistically significant. All the four obturation techniques showed presence of voids with no significant difference.ConclusionBoth Lentulo spiral and Past inject carrier were equally efficient in attaining an optimally filled homogenous obturation in deciduous teeth.How to cite this articleRaju SS, Reddy RE, Rani TS, et al. Assessment of Four Obturation Methods in Deciduous Teeth Using Digital Radiography: An In Vivo Study. Int J Clin Pediatr Dent 2022;15(S-1):S52-S56.

A Comparative Research on Corrosion Behavior of Electroplated and Magnetron Sputtered Chromium Coatings

Chromium deposits rank among the most widespread metal coatings for functional and decorative purposes. However, electrodeposition from Cr(VI) aqueous solution, which is the industrial process currently used to achieve thin chromium deposits, presents several environmental issues, urging the development of alternative solutions. In this study, which aims to compare the functional and aesthetical properties of decorative coatings, 800 nm thick chromium layers were deposited directly onto copper substrates by means of magnetron sputtering (MS) and direct current electrodeposition (ED). The obtained coatings were characterized regarding their thickness, morphology, color index, chemical composition, and corrosion resistance viewpoints. With respect to the electroplated samples, which constitute the benchmark, the magnetron sputtered ones appeared to be darker but showed a pleasing reflective appearance and superior thickness homogeneity, as well as the absence of voids and macrocracks, as evidenced by scanning electron microscopy (SEM) investigation. Regarding the anticorrosion performances of the chromium layers, electrochemical and standard salt spray test (NSS test) were carried out at room temperature in 3.5% NaCl solution, and evidenced similar, if not better, results for the magnetron sputtered coatings. On the whole, the data displayed here demonstrates the suitability of magnetron sputtering technology for use as an industrially feasible finishing technology for both aesthetic and mild-condition anticorrosion purposes.

Cone-beam Computed Tomographic Evaluation of the Quality of Obturation Using Different Pediatric Rotary File Systems in Primary Teeth.

Aim and objectiveTo compare and evaluate the efficacy of three different pediatric rotary file systems in primary molars using cone-beam computed tomography (CBCT).Materials and methodsThirty extracted mandibular primary molars were selected and divided into three groups with ten teeth each, instrumented with Kedo SG Blue rotary files, Pro AF Baby gold rotary files, and Pedo Flex rotary files, respectively. Root canal obturation was done with zinc-oxide eugenol cement and the quality of obturation was assessed using CBCT based on the extent of filling as underfilled or optimally filled and the presence or absence of voids within the filling. The data were statistically analyzed using the Chi-square test.ResultsAmong the three groups, the Kedo SG Blue group showed more number of optimally filled teeth with minimal voids (p < 0.05) followed by the Pro AF Baby gold group and Pedo Flex group.ConclusionWithin the study limitations, the Kedo SG Blue group showed ideal endodontic obturation when compared with Pro AF baby gold and Pedo Flex rotary file systems.Clinical significanceThe present study will guide the pedodontists regarding the efficacy of pediatric rotary file systems and their usage protocols.How to cite this articleVaishali Naidu D, Sharada Reddy J, Patloth T, et al. Cone-beam Computed Tomographic Evaluation of the Quality of Obturation Using Different Pediatric Rotary File Systems in Primary Teeth. Int J Clin Pediatr Dent 2021;14(4):542–547.

Influence of Solvents on Properties of ZnS Thin Films Synthesized by Chemical Spray Pyrolysis Technique

Abstract: In this paper, the influence of solvents on the structural, optical, surface and electrical properties of spray-deposited ZnS thin films has been studied. Different precursor mixtures were prepared from ethylene glycol, deionized water and alcohol solvents and sprayed on heated glasses via a simple and cost-effective technique known as spray pyrolysis. XRD patterns confirmed cubic and tetragonal phases of synthesized ZnS material. The optical analysis of the synthesized ZnS films showed that films prepared using ethylene glycol solvent have the highest transmittance and the best bandgap (3.61 eV). Surface morphology showed the absence of voids and pinholes in the Scanning Electron Micrograph of ZnS film prepared from ethylene glycol and electrical studies showed that ZnS films prepared using the same solvent have the lowest resistivity. Keywords: ZnS, Thin film, Spray pyrolysis, Bandgap, Morphology.

Synthesis, characterization, and incorporation of upconverting nanoparticles into a dental adhesive.

The purpose of this study was to describe the synthesis, characterization, and functionalization of b-NaYF4:30%Yb/0.5%Tm upconverting nanocrystals for use as nanofillers in a dental adhesive and microscopically evaluate the interface between the particles and a commercial adhesive. The upconverting nanoparticles were synthesized and purified by thermal decomposition, and their chemical composition determined by energy dispersive X-Ray spectroscopy. The crystalline structure was characterized using X-Ray diffraction and morphology and size were observed with scanning and transmission electron microscopy. Upconverting emission was evaluated by spectrophotometry irradiating the particles with a 975 nm diode laser. Particles were functionalized with polyacrylic acid and the success was confirmed by measurement of Zeta Potential and transmission electron microscopy. The results of X-ray diffraction found a pure hexagonal phase crystalline pattern. Scanning electron microscopy showed uniform dispersion of hexagonal-shaped particles of approximately 150 nm. Upconversion emission was observed in 344 nm, 361 nm, 450 nm, 474nm, 646 nm, 803 nm. Functionalization success was confirmed by formation of a stable aqueous colloid with a Zeta potential of -29.5mV and the absence of voids in the particle-adhesive interface on the transmission electron microscopy images. The reported synthesis and functionalization process produced upconverting nanoparticles emitting photons within the blue spectral region (450 nm and 474 nm).

Manufacturing and characterization of continuous fiber-reinforced thermoplastic tape overmolded long fiber thermoplastic

Light-weight construction, design freedom, integration of functions, and compelling cost element are desired by Original Equipment Manufacturers (OEMs) and their suppliers. The emergence of overmolding of continuous-discontinuous reinforcement enables design freedom and ability to tailor stiffness, strength, and damage tolerance for structural applications. In this work, long fiber thermoplastics (LFT) are overmolded with continuous fiber-reinforced thermoplastic (CFRTP) tape are combined using extrusion compression molding process to evaluate the structural performance. The CFRTP tape overmolded LFT samples were characterized using nondestructive and destructive techniques to track fiber alignment, fiber distribution, manufacturing defects, interfacial bonding of the tape – LFT and effect of CFRTP tape on LFT. Mode 1 fracture toughness, G1c for tape overmolded LFT was higher by 25–30% compared to literature reported G1c. This response was attributed to excellent fiber distribution, good fiber wetting, and absence of voids at the interface. Three-point bend test indicated that CFRTP tape overmolded LFT composites were better able to resist damage under the bending load compared to constituent LFT composite. Flexural strength of the overmolded composite was higher by 119–142%, and modulus higher by 77–65% compared to constituent LFT composite. Simulated flexural results accurately represents the mechanical behavior of composites. The penetration energy of tape overmolded LFT composites determined by LVI test was in the range of 27.66–30.15 J, which is significantly higher than constituent LFT composite, 7.76 J. CFRTP tape overmolded LFT composite exhibits progressive fiber fracture, matrix cracking, and interfacial debonding failure, whereas, constituent LFT composite showed catastrophic fiber fracture.

Success Rate of Obturation of Root Canals by Different Techniques in Primary Molars: A Comparative Clinical Study

Objective: To compare the success rate of different obturation procedures in primary mandibular second molars clinically and also by digital radiovisiography. Methods: A total of 40 children aged between 4-8 years with deeply carious mandibular second primary molars indicated for single session pulpectomy were selected. Canals were obturated with Metapex. The 3 study groups (Endodontic plugger, Handheld lentulospiral, Navi Tip syringe) were compared with the control group (reamer) both clinically and radiovisiographically. The data collected were statistically analyzed using Pearson’s Chi-square and Fisher’s exact test. Results: The use of Navi tip syringe led to the least number of voids followed by Endodontic plugger and Reamer and the highest number of voids was reported with Lentulospiral. Navitip presented maximum number of optimally filled cases followed by Endodontic plugger and Lentulospiral and least number of optimally filled cases with reamer. However, there was no statistically significant difference (p&gt;0.05) in any of the groups with clinical (pain and tenderness to percussion) and radiographic parameters (presence or absence of voids and length of obturation). Conclusion: Within the limitations of the present study, though the clinical outcome was statistically insignificant, Navitip syringe exhibited encouraging results and is a promising option for obturation in primary teeth.

Comparison of the wear and corrosion behavior between CrN and AlCrN coatings deposited by Arc-PVD method

In this investigation, we studied deposition of chromium nitride (CrN) and aluminum chromium nitride (AlCrN) coatings on the steel substrate by using cathodic arc evaporation technique (Arc-PVD). Therefore, the wear and corrosion behavior of the CrN and AlCrN coatings were compared. Applying cathodic arc evaporation at 200 °C for 90 min led to a coating with approximately 2 micrometers thickness. In order to compare the properties of CrN and AlCrN coatings, all of the Arc-PVD methods coating parameters were kept at a constant value within the deposition of coating having the duty cycle of 50 percent, bias voltage of −100 V, and the target current of 100 A. For characterizing the crystal structure and microstructure of the coatings, x-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) were utilized. In order to evaluate the coatings adhesion and the wear behavior, Rockwell-C indenter and the pin-on-disk test were used, respectively. Moreover, a potentiodynamic polarization device was used in 3.5% NaCl solution for studying the corrosion behavior of the coatings. The results revealed that CrN coating has the lower friction coefficient but AlCrN coating showed better wear resistance. Also, CrN coating had a better corrosion resistance than AlCrN on account of the uniform surface morphology and the absence of void which protects the substrate from the corrosive medium.

Comparative Evaluation of Three Obturating Techniques in Primary Molars: An in Vivo Study.

Objectives: The purpose of this study was to evaluate and compare the quality of obturation between the two tested methods for root canal filling with a newer system in primary teeth. Study design: A total of 104 canals were prepared and obturated using zinc oxide eugenol paste. The three delivery systems compared were: Rotary lentulospiral and Navitip® withNavitip® Double Sideport. Radiographs were used to evaluate the canals for length of obturation and presence of voids. Results: The data were analyzed using chi-square tests. Significant differences was seen between the three groups for the presence of voids (p value =0.042) with less voids in Navitip® Double Sideport. There were no difference between the three groups for the extent of filling (p value=0.170). Conclusion- Navitip® Double Sideport showed the better results in terms of extent of obturation and absence of voids when compared to the Rotary lentulospiral and Navitip®.

Energy and Eco-Sustainability using Pressure-less Silver Sintering for RF Power Electronics

Abstract Energy &amp; Eco-Sustainability using Pressureless Silver Sintering for RF Power Electronics A virtually void free die attach was successfully achieved using a fixed but critical volume of Ag sinter paste by a process of pressureless sintering on a multi-axis cartesian style bonder, retro-fitted with with a high-speed jetting dispenser. While this process potentially offered an ideal combination of cost-effectiveness, control and speed, it required the development of additional software protocols to secure the level of performance demanded of the dispenser to meet exacting technical requirements. This proprietary adaptation we term “Fixed BLT” software, and over five test pieces we were consistently able to deliver a fixed height bond-line of circa 70% of bond height, translating as 50 um before sinter and 30 um after. In each case the result was a virtually bond free void secured in a timely, repeatable, commercially effective manner. The absence of voids was verified through industry standard non-destructive analysis utilizing confocal scanning acoustic microscopy (CSAM).

Voids in walls of mesoporous TiO2 anatase nanotubes by controlled formation and annihilation of protonated titanium vacancies

Amorphous TiO2 nanotubes (TNTs) grown anodically on Ti metal in aqueous electrolytes show a crystallization behaviour strongly dependent on the atmosphere used during annealing at high temperature. In wet oxidizing conditions, the amorphous TNTs walls transform into relatively large and well crystallized anatase-like domains permeated by prismatic voids. On the other hand, crystallization of the amorphous nanotubes under dry reducing conditions induces nanocrystalline aggregates that do not show prismatic voids and exhibit different electronic properties. Supported by density functional theory calculations, it is argued that the formation or absence of voids can be understood in terms of formation and condensation of protonated titanium vacancies. Tunable morphology through defect chemical engineering as such, enables TNTs with increased surface area and catalytic activity, which find potential application in supercapacitors, sensors, photocatalysis, photoelectrochemistry, and dye-sensitized solar cells.

Significantly enhancing the strength + ductility combination of Mg-9Al alloy using multi-walled carbon nanotubes

In the present study, Mg-9Al/MWCNTs (multi-walled carbon nanotubes) composites were synthesized using the technique of powder metallurgy followed by hot extrusion. MWCNTs were dispersed in Mg-9Al matrix using an ionic gemini dispersant. Microstructural characterization studies revealed that MWCNTs can be individually dispersed with no structural damage. Matrix-MWCNT was found to be excellent (absence of voids and debonding). Results further revealed that the addition of MWCNTs significantly affected the size of Mg17Al12 phase, which decreased from micron to nano length scale. The tensile test results revealed that the elongation and ultimate tensile strength of Mg-9Al composite with 0.4 wt % MWCNTs content were 15% and 355 MPa, respectively, showing 150% and 18% enhancement in comparison to Mg-9Al alloy. The remarkably enhanced mechanical properties were mainly attributed to the uniformly distributed nanoscale Mg17Al12 s phase in composite and the excellent interface bonding between MWCNTs and matrix.

Experimental analysis of one-way composite steel deck slabs voided by circular paper tubes: Shear strength and moment–shear interaction

In order to improve structural efficiency, environmental performance, and constructability, a new type of one-way composite voided slab system (TUBEDECK) has been recently proposed which combines profiled steel decks with cast-in-situ RC slabs. Because eliminating concrete volume to optimize flexural strength can significantly reduce the shear strength of nonprestressed concrete or composite slabs without shear reinforcement, a clarification of the shear resistance capacity is required. In this study, shear tests on a total of 12 specimens were conducted with slab thickness, the presence or absence of voids and/or steel decks, and tension reinforcement ratio as variables. The results show that combined flexure and shear dominated the behavior of both voided (V) slabs and TUBEDECK (TD) slabs, and web-shear cracking did not affect strength. Predicted shear strength based on the minimum web width was too conservative. Conversely, the shear strength prediction equations, which were proposed on the basis of the real cross-sectional area of concrete, predicted the capacity of both V slabs and TD slabs from a reasonably conservative perspective. A discussion on the influence of moment–shear interaction is also included, and an interaction design model is proposed in a further investigation.

Electrical conductivity, mechanical strength and corrosion characteristics of spark plasma sintered Al-Nb nanocomposite

An experimental study of the microstructure, electrical conductivity, corrosion characteristics and mechanical strength of Al-Nb nanocomposite consolidated via spark plasma sintering was the focus of this work. The start-up powders as well as the sintered samples were characterised with X-ray diffractometer, transmission electron microscopy and field-emission scanning electron microscope equipped with energy dispersive X-ray spectroscopy. The microhardness of the sintered samples was tested with Vickers hardness tester. The polarisation test was carried out with Potentiostat Autolab. The electrical conductivity was tested with four-point probe meter. The microstructural results showed homogenous dispersion of Nb reinforcement in the matrix, no grain growth and absence of voids. Good corrosion characteristics were achieved with Al-1Nb and Al-4Nb composites while the highest microhardness of 420 MPa and tensile strength of 138 MPa were obtained with Al-4Nb. The electrical conductivity increased from 38.9 to 40.1% IACS with Al-8Nb. The improved properties were as a result of the optimal sintering parameters, good fabrication attributes of SPS and the synergistic effects of Al and Nb.

Factors Affecting the Outcome of Non-Surgical Endodontic Treatments Performed by Undergraduate Students in a Greek Dental School.

Objective:To evaluate the outcome of initial endodontic treatments performed by undergraduate students in a Greek dental school and to determine the factors that may impact the treatment outcome.Methods:From a randomly selected sample of 677 non-surgical endodontic treatments performed between 2012 and 2015, follow-up appointments were scheduled with patients whose dental records matched the inclusion criteria. After clinical and radiographic examination, the treatment outcome was classified as ‘success’ (healed/healing) or ‘failure’ (uncertain/unsatisfactory healing). The statistical analysis of the data was performed using generalized estimating equations. Intra-examiner and inter-examiner agreements were checked with the intraclass correlation coefficient and with Cohen’s kappa. The statistical significance level was set at P<0.05.Results:A total of 244 teeth (349 roots) were included for further analysis, and the mean follow-up period was 2.8 years. Overall, the success rate for the treated roots was 72.8%. Μultivariate analysis revealed four decisive factors as having a positive impact on the outcome, namely, the absence of voids within the root fillings (P<0.001), the absence of pre-operative periapical lesions (P=0.001), the extension of the root filling material by 0-2 mm from the radiographic apex (P<0.001) and the root type (anterior roots: P=0.015 and premolar roots: P=0.011). The association of gender, arch, pulp status and type of coronal restoration with the outcome was not statistically significant (P>0.05). Moreover, when the outcome according to pre-operative periapical status and the technical variables of root fillings (apical extension and density) was investigated, roots without periapical lesion, with a root filling material extended 0-2 mm within the apex and without voids revealed the highest success rate (94.5%).Conclusion:The success rate of non-surgical endodontic treatments performed in a Greek dental school was in the range of those reported in other studies. The pre-operative periapical status, technical variables of root fillings (apical extension and density) and root type were regarded as significant prognostic factors of the outcome.

Advanced Statistical Analyses to Reduce Inconsistency of Bond Strength Data

This study was designed to clarify the interrelationship of factors that affect the value of microtensile bond strength (µTBS), focusing on nondestructive testing by which information of the specimens can be stored and quantified. µTBS test specimens were prepared from 10 noncarious human molars. Six factors of µTBS test specimens were evaluated: presence of voids at the interface, X-ray absorption coefficient of resin, X-ray absorption coefficient of dentin, length of dentin part, size of adhesion area, and individual differences of teeth. All specimens were observed nondestructively by optical coherence tomography and micro–computed tomography before µTBS testing. After µTBS testing, the effect of these factors on µTBS data was analyzed by the general linear model, linear mixed effects regression model, and nonlinear regression model with 95% confidence intervals. By the general linear model, a significant difference in individual differences of teeth was observed (P < 0.001). A significantly positive correlation was shown between µTBS and length of dentin part (P < 0.001); however, there was no significant nonlinearity (P = 0.157). Moreover, a significantly negative correlation was observed between µTBS and size of adhesion area (P = 0.001), with significant nonlinearity (P = 0.014). No correlation was observed between µTBS and X-ray absorption coefficient of resin (P = 0.147), and there was no significant nonlinearity (P = 0.089). Additionally, a significantly positive correlation was observed between µTBS and X-ray absorption coefficient of dentin (P = 0.022), with significant nonlinearity (P = 0.036). A significant difference was also observed between the presence and absence of voids by linear mixed effects regression analysis. Our results showed correlations between various parameters of tooth specimens and µTBS data. To evaluate the performance of the adhesive more precisely, the effect of tooth variability and a method to reduce variation in bond strength values should also be considered.