Manual Milling Research Articles

Experimental Investigation of the Surface Roughness for Aluminum Alloy AA6061 in Milling Operation by Taguchi Method with the ANOVA Technique

The surface roughness of the machined parts is the most important parameter to predict the performance of mechanical components. Moreover, predicting the optimal machining parameters conditions is the preferable method for cost reduction and achieving the desired surface quality of the product. This study investigates three cutting parameters, such as depth of cut, spindle speed, and feed for the milling aluminium alloy AA6061, to predict the surface roughness quality. The experimental work utilized a manual milling machine with a coated carbide cutter. Furthermore, the experiments were arranged using the Taguchi L9 orthogonal array (OA) method. The average surface roughness (Ra) was measured and converted to signal-to-noise (S/N) ratio and then analyzed in the statistical method of analysis of variance (ANOVA). Finally, the optimal combination set speed, feed, and depth of cut was 2400 rpm, 30 mm/min, and 0.5 mm, respectively. Also, according to the ANOVA test, the most influential parameter was the spindle speed among the selected parameters, with the highest P value of (66.42%). In comparison, the lowest P value is a depth of cut (5.34%). Furthermore, spindle speed was the only significant factor statistically. By selecting a high spindle speed (2400 rpm), surface quality was enhanced, but the preferable level was low for depth of cut and feed.

Carbonation of hydrated cement: The impact of carbonation conditions on CO2 sequestration, phase formation, and reactivity

The efficiency of hydrated cement carbonation is often ascribed to the total amount of CO2 stored by the material. However, the morphology and composition of silicate phases upon carbonation are equally important to unseal the pozzolanic potential of cement recycling for sustainable growth. Therefore, the current study investigates the impact of aqueous- and dry-carbonation (AC and DC) on polymorph formation, silicate microstructure, and porosity of CEM-I as well as CEM–III–derived pastes. The limited diffusion of calcium ions during DC gives rise to the formation of a carbonate shell comprised of calcite, aragonite, and vaterite and results in a 15% lower carbonation efficiency compared to AC. Manual milling was required to expose the amorphous silicate gel and allow for optimal reactivity. AC in 0.1 M sodium hydroxide was found to be the most efficient carbonation method for both reactivity and CO2 sequestration. Sodium hydroxide allowed for an increased CO2 capture and thereby promoted rapid carbonation and the formation of a highly porous silicate phase. The presence of sodium hydroxide promotes decalcification but is postulated to limit the pozzolanic reactivity. Although a high calcium content allows for high CO2 sequestration in CEM-I, for better pozzolanic reactivity a silica-rich material like CEM-III is recommended.

BIOGAS PRODUCTION BY ANAEROBIC DIGESTION OF COFFEE HUSKS AND CATTLE MANURE

The use of agricultural residues in anaerobic digestion (AD) for biogas production promotes environmental and socioeconomic benefits. This study aimed to evaluate the biogas production from dry coffee husks (DCH), wet coffee husks (WCH), and cattle manure (CM) in AD. Prototypes of Indian anaerobic benchtop digesters with a batch feeding system supplied with 100 CM, 100 DCH, and 100 WCH for anaerobic mono-digestion (AMoD) and 25:75 DCH:CM and WCH:CM for anaerobic co-digestion (ACoD) were used in the experiment. The dry husk was mechanically pre-treated with grinding in a manual mill. Moisture and total solid presented no statistically significant difference between the studied relationships but the coffee husk as a co-digestant acidified the medium to be digested. The 25:75 DCH:CM ratio anticipated biogas production (7th week) and showed higher potential for weekly and accumulated biogas production. The Gompertz model showed the best fit considering the coefficient of determination, mean relative error, standard deviation of the estimate, and mean squared deviation. Therefore, the coffee husk as a co-digestant of cattle manure is a potential lignocellulosic biomass for biogas production provided that the process is conducted under pre-treatment.

Efficacy of Virtual Equipment Training

The University of Ottawa faculty of engineering, in Ottawa Canada, is home to multiple rapid prototyping facilities as well as entrepreneurship spaces. This includes a makerspace, a machine shop and a design space for any student to use free of charge. Due to COVID-19 the spaces were either shut down or running virtual activities where possible. In the absence of any significant virtual content for learners, virtual computer simulations and virtual reality simulations were developed for various technologies including a manual mill and lathe, a laser cutter and soldering. Even as the COVID-19 restrictions are being lifted, the virtual simulations will be used as a pre-training introduction for in-person sessions. This paper aims to understand how well the virtual training simulations compare and compliment the in-person training for different equipment. Factors considered are the level of previous knowledge and level of interest in the equipment. The same assessment will be given to 3 groups of participants: those who have only done the virtual training, who have only done the in-person training and who have done both. The results from each group will be compared and analyzed to determine the efficacy of the virtual simulation and what advantages it has as a pre-training resource.

Innovative robotization of manual manufacturing processes

Manufacturing industries are continually challenged to adapt to a competitive environment. Consequently, there is an urgency to opt for automation technologies to upgrade their manufacturing facilities and make them more flexible. Especially this relates to automating manual manufacturing processes, which is often challenging to structure to ensure repetitiveness and generalization to other processes within the facility. Consequently, innovating systematic approaches to identify robotization opportunities is an interesting proposition for manufacturing set-ups that would like to integrate collaborative robots on the shop floor and struggle with the decision steps to follow.In this paper, a framework for supporting robotization effort for manufacturing set-ups is proposed. The methodology consisting of five phases, culminating in the identification of robotization opportunities. A case for manual milling manufacturing processes is demonstrated as a ‘proof-of-concept’. The first step of the proposed approach focuses on task decomposition, in which manual manufacturing tasks are characterized. This is followed by task allocation to a robot and human agent based on intrinsic characteristics of the task to capabilities of the agent. Next, alternative layout configurations for candidate cell layouts are generated. In the final step, a candidate layout is selected and modeled in an agent-based simulation platform, considering factors such as realism, interaction safety between the robot and human agent, and interesting manufacturing metrics such as resource utilization and throughput rate. A final configuration is optimized, which visualizes a collaborative robot performs loading and unloading tasks alongside an operator performing highly cognitive tasks. For safety, zoning of the manufacturing cell is visualized, considering a working area separated by a safety fence.

Microbial yield from infectious tissues pretreated by various methods: an invitro study

BackgroundThis study aimed to evaluate the effects of different pretreatment methods on the microbial yield from infectious tissues.MethodsStrains of Staphylococcus aureus (SA), Escherichia coli (EC) and Candida albicans (CA) were used to construct single-surface, full-surface, and internal infection models in sterile pork tissue. Manual milling (MM), mechanical homogenization (MH), sonificated (SF), dithiothreitol (DTT), and direct culture (DC) were used to pretreat these tissues, the microbial yield from different pretreatment methods were recorded and compared. Moreover, periprosthetic tissues collected intraoperatively from periprosthetic joint infection (PJI) patients were used as a verification.ResultsThe study showed that the microbial yield from MH pretreatment was significantly higher than that of MM (P < 0.01) and SF pretreatment method (P < 0.01). Furthermore, in the internal infection model, the microbial yield from MH group was also significantly higher than that of SF (P < 0.01), DTT (P < 0.01), and DC group (P < 0.01). Moreover, the number of bacterial colonies obtained from periprosthetic tissues pretreated by MH was significantly higher than pretreated by other pretreatment methods (P = 0.004).ConclusionsThe effects of MH and DTT in microbial yield were significantly higher than that of DC, SF and MM, and these methods can be used to process multiple tissue samples at the same time, which might further improve the diagnostic sensitivity of infectious disease.

Usability of cooperative surgical telemanipulation for bone milling tasks

PurposeCooperative surgical systems enable humans and machines to combine their individual strengths and collaborate to improve the surgical outcome. Cooperative telemanipulated systems offer the widest spectrum of cooperative functionalities, because motion scaling is possible. Haptic guidance can be used to assist surgeons and haptic feedback makes acting forces at the slave side transparent to the operator, however, overlapping and masking of forces needs to be avoided. This study evaluates the usability of a cooperative surgical telemanipulator in a laboratory setting.MethodsThree experiments were designed and conducted for characteristic surgical task scenarios derived from field studies in orthopedics and neurosurgery to address bone tissue differentiation, guided milling and depth sensitive milling. Interaction modes were designed to ensure that no overlapping or masking of haptic guidance and haptic feedback occurs when allocating information to the haptic channel. Twenty participants were recruited to compare teleoperated modes, direct manual execution and an exemplary automated milling with respect to usability.ResultsParticipants were able to differentiate compact and cancellous bone, both directly manually and teleoperatively. Both telemanipulated modes increased effectiveness measured by the mean absolute depth and contour error for guided and depth sensitive millings. Efficiency is decreased if solely a boundary constraint is used in hard material, while a trajectory guidance and manual milling perform similarly. With respect to subjective user satisfaction trajectory guidance is rated best for guided millings followed by boundary constraints and the direct manual interaction. Haptic feedback only improved subjective user satisfaction.ConclusionA cooperative surgical telemanipulator can improve effectiveness and efficiency close to an automated execution and enhance user satisfaction compared to direct manual interaction. At the same time, the surgeon remains part of the control loop and is able to adjust the surgical plan according to the intraoperative situation and his/her expertise at any time.

Precision of Hole-Drilling Residual Stress Depth Profile Measurements and an Updated Uncertainty Estimator

Measurement precision and uncertainty estimation are important factors for all residual stress measurement techniques. The values of these quantities can help to determine whether a particular measurement technique would be viable option. This paper determines the precision of hole-drilling residual stress measurement using repeatability studies and develops an updated uncertainty estimator. Two repeatability studies were performed on test specimens extracted from aluminum and titanium shot peened plates. Each repeatability study included 12 hole-drilling measurements performed using a bespoke automated milling machine. Repeatability standard deviations were determined for each population. The repeatability studies were replicated using a commercially available manual hole-drilling milling machine (RS-200, Micro-Measurements). An updated uncertainty estimator was developed and was assessed using an acceptance criterion. The acceptance criterion compared an expected percentage of points (68%) to the fraction of points in the stress versus depth profile where the measured stresses ± its total uncertainty contained the mean stress of the repeatability studies. Both repeatability studies showed larger repeatability standard deviations at the surface that decay quickly (over about 0.3 mm). The repeatability standard deviation was significantly smaller in the aluminum plate (max ≈ 15 MPa, RMS ≈ 6.4 MPa) than in the titanium plate (max ≈ 60 MPa, RMS ≈ 21.0 MPa). The repeatability standard deviations were significantly larger when using the manual milling machine in the aluminum plate (RMS ≈ 21.7 MPa), and for the titanium plate (RMS ≈ 18.9 MPa). The single measurement uncertainty estimate met a defined acceptance criterion based on the confidence interval of the uncertainty estimate.

An augmented reality-based training system with a natural user interface for manual milling operations

This study developed an augmented reality (AR)-based training system for conventional manual milling operations. An Intel RealSense R200 depth camera and a Leap Motion controller were mounted on an HTC Vive head-mounted display to allow users freely walk around in a room-size AR environment to operate a full-size virtual milling machine with their barehands, using their natural operation behaviors, as if they were operating a real milling machine in the real world, without additional worn or handheld devices. GPU parallel computing was used to handle dynamic occlusions and accelerate the machining simulation to achieve a real-time simulation. Using the developed AR-based training system, novices can receive a hands-on training in a safe environment, without any injury or damage. User test results showed that using the developed AR-based training resulted in lower failure rates and inquiry times than using video training. Users also commented that the AR-based training was interesting and helpful for novices to learn the basic manual milling operation techniques.

The mechanochemical route of vaterite synthesis using sodium hexametaphosphate as an inorganic additive

AbstractVaterite is a metastable phase of CaCO3 and was prepared mechanochemically for the first time with the assistance of sodium hexametaphosphate (SHMP). First, CaCO3 was prepared without SHMP and was characterized using X‐ray diffraction (XRD) to study the effect of milling times and speeds on the polymorphs of product. The results indicate that the reaction is complete at 60 minutes producing only calcite. Additionally, amorphous CaCO3 (ACC) was obtained at a milling speed of 300 rpm, while calcite was obtained at 600 and 1000 rpm. Then, the effect of SHMP concentration on the fraction of vaterite was investigated, and the vaterite fraction increased with increasing SHMP amount. Subsequently, the effect of milling speed in the presence of 0.8 g of SHMP was studied, and the vaterite fraction increased with decreasing milling speed. Finally, gentler manual milling was employed, and the effect of the amount of added SHMP on vaterite formation was evaluated. The results confirmed that vaterite increased with increasing amounts of SHMP, and that vaterite formed more readily via manual milling than via mechanical milling. Observations with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that calcite and vaterite particles formed by mechanical milling were irregular agglomerates composed of primary nanoparticles while calcite particles formed by manual milling were irregular microparticles. Moreover, vaterite readily aggregated into spherical particles as the amount of SHMP increased. To investigate the reaction process and mechanism, the ethanol‐washed product was characterized using XRD, SEM/EDS and TEM/SAED. The results demonstrate that ACC and calcite were concomitant during the milling process, and ACC transformed into vaterite during subsequent water washing.

Synthesis at room atmosphere conditions of phosphorescent emitter SrAl2O4:Eu,Dy

In this investigation strontium aluminate phosphors (SrAl2O4:Eu,Dy) were synthesized through two modified routes, sol-gel method (route of Pechini) and molten salts (activated by mechanosynthesis). The slight modifications allow to use lower temperatures and shorter times of thermal treatments than those typically used. Moreover, the synthesis is performed under a simple air atmosphere. The intermediates identified during the synthesis by sol gel are: polyesters, probably coordinated to metallic ions, the cubic Pb[NO3]2-type structure of Sr(NO3)2, and the orthorhombic aragonite-type structure of SrCO3. The intermediates identified during the synthesis by molten salts are: highly crystalline NaNO3 (obtained by the manual milling of reactants), the monoclinic bayerite-type structure of Al(OH)3 and the orthorhombic aragonite-type structure of SrCO3. The results of the characterization of these intermediates provided worthy information to propose the experimental conditions of reaction. The XRD characterization of products, obtained by both methods, shows the monoclinic stuffed tridymite-type structure of SrAl2O4 as predominant polycrystalline phase with a calculated mean particle size of ~26 nm. Transmission electron micrographs reveal particles with different morphology and broad distribution of sizes. HRTEM images discard the presence of amorphous phases and SAED patterns corroborate the presence of the crystalline phases previously identified by XRD. The persistent afterglow emission is centered close to the white light with a dominant wavelength of 550 nm and purity color of 0.45. The persistent emission lifetime is similar, at around 7 min, value that is sufficient for bio-imaging or security codes applications.

Comparative analysis of asphalt concrete mixtures employing pebbles and synthetic coarse aggregate of calcined clay in the Amazon region

ABSTRACTSeveral parts of the Amazon region present high costs concerning to pavement services, mainly because of their geological condition where there is a lack of rocky material. In these areas, natural pebble deposits or stone quarries are very distant from the consumption locations. The frequently used coarse aggregate in the State of Amazonas, Brazil, is the pebble taken from the riverbeds, with an at least 500 km distance from the greatest consumption centre, resulting in a high transportation fee which approaches in about 50% of the final product cost. Searching for an alternative and non-conventional material which could replace the pebbles, the natural clay was studied due to its mineral abundance in the Amazon region. The production process adopted by the ceramic industry was reproduced in laboratory tests, in a handcrafted way, using a manual mill composed by four nozzles with dimensions of 12.7, 9.5, 4.8 and 2.0 mm. The wet aggregates were calcinated at temperatures of 780, 850, 950, 1050 and 1150 °C, and physically characterised. It was made a comparative analysis between the conventional hot mixed asphalt concrete (with pebbles) and using synthetic aggregates, studying several physical and mechanical parameters. Asphalt mixtures made with synthetic aggregates offered better bonding between their components when compared with those made with pebbles, favouring gain in mechanical resistance, since they represented a structural skeleton more resistant than pebbles. In addition, as the firing temperature of the synthetic aggregates increased, the consumption of asphalt cement decreased, due to the phase transformations of the crystal to the amorphous phase. The results of the resilient modulus to static indirect tensile strength ratios allowed to infer that asphalt mixtures made with synthetic aggregates point to a longer fatigue life when compared to the pebble mixture principally at values lower than 3500.

Cadaveric Testing of Robot-Assisted Access to the Internal Auditory Canal for Vestibular Schwannoma Removal.

An image-guided robotic system can safely perform the bulk removal of bone during the translabyrinthine approach to vestibular schwannoma (VS). The translabyrinthine approach to VS removal involves extensive manual milling in the temporal bone to gain access to the internal auditory canal (IAC) for tumor resection. This bone removal is time consuming and challenging due to the presence of vital anatomy (e.g., facial nerve) embedded within the temporal bone. A robotic system can use preoperative imaging and segmentations to guide a surgical drill to remove a prescribed volume of bone, thereby preserving the surgeon for the more delicate work of opening the IAC and resecting the tumor. Fresh human cadaver heads were used in the experiments. For each trial, the desired bone resection volume was planned on a preoperative computed tomography (CT) image, the steps in the proposed clinical workflow were undertaken, and the robot was programmed to mill the specified volume. A postoperative CT scan was acquired for evaluation of the accuracy of the milled cavity and examination of vital anatomy. In all experimental trials, the facial nerve and chorda tympani were preserved. The root mean squared surface accuracy of the milled cavities ranged from 0.23 to 0.65 mm and the milling time ranged from 32.7 to 57.0 minute. This work shows feasibility of using a robot-assisted approach for VS removal surgery. Further testing and system improvements are necessary to enable clinical translation of this technology.

The biomechanical strength of a hardware-free femoral press-fit method for ACL bone-tendon-bone graft fixation.

The purpose was to investigate graft slippage and ultimate load to failure of a femoral press-fit fixation technique for anterior cruciate ligament (ACL) reconstruction. Nine fresh-frozen knees were used. Standardized harvesting of the B-PT-B graft was performed. The femora were cemented into steel rods, and a tunnel was drilled outside-in into the native ACL footprint and expanded using a manual mill bit. The femoral bone block was fixed press-fit. To pull the free end of the graft, it was fixed to a mechanical testing machine using a deep-freezing technique. A motion capture system was used to assess three-dimensional micro-motion. After preconditioning of the graft, 1000 cycles of tensile loading were applied. Finally, an ultimate load to failure test was performed. Graft slippage in mm ultimate load to failure as well as type of failure was noted. In six of the nine measured specimens, a typical pattern of graft slippage was observed during cyclic loading. For technical reasons, the results of three knees had to be discarded. 78.6% of total graft slippage occurred in the first 100 cycles. Once the block had settled, graft slippage converged to zero, highlighting the importance of initial preconditioning of the graft in the clinical setting. Graft slippage after 1000 cycles varied around 3.4±3.2mm (R=1.3-9.8mm) between the specimens. Ultimate loading (n=9) revealed two characteristic patterns of failure. In four knees, the tendon ruptured, while in five knees the bone block was pulled out of the femoral tunnel. The median ultimate load to failure was 852N (R=448-1349N). The implant-free femoral press-fit fixation provided adequate primary stability with ultimate load to failure pull forces at least equal to published results for interference screws; hence, its clinical application is shown to be safe.

Impact of milling, enzyme addition, and steam explosion on the solid waste biomethanation of an olive oil production plant.

Anaerobic digestion is a consolidated bioprocess which can be further enhanced by incorporating an upstream pretreatment unit. The olive oil production produces a large amount of solid waste which needs to be properly managed and disposed. Three different pretreatment techniques were evaluated in regard to their impact on the anaerobic biodegradability: manual milling of olive pomace (OP), enzyme maceration, direct enzyme addition, and thermal hydrolysis of two-phase olive mill waste. The Gompertz equation was used to obtain parameters for comparison purposes. A substrate/inoculum ratio 0.5 was found to be the best to be used in anaerobic batch test with olive pomace as substrate. Mechanical pretreatment of OP by milling increases the methane production rate while keeping the maximum methane yield. The enzymatic pretreatment showed different results depending on the chosen pretreatment strategies. After the enzymatic maceration pretreatment, a methane production of 274 ml CH4 g VS added (-1) was achieved, which represents an improvement of 32 and 71 % compared to the blank and control, respectively. The direct enzyme addition pretreatment showed no improvement in both the rate and the maximum methane production. Steam explosion showed no improvement on the anaerobic degradability of two-phase olive mill waste; however, thermal hydrolysis with no rapid depressurization enhanced notoriously both the maximum rate (50 %) and methane yield (70 %).

Sustainability assessment of products based on fuzzy multi-criteria decision analysis

Sustainable product design is one of the key challenges for manufacturers to achieve sustainability, whereas it is not clear what products mean sustainability due to subjectivity of concept. This paper proposes a novel assessment methodology for evaluating product sustainability performance based on quantitative and qualitative information. Product sustainability performance index (PSPI) is defined to assist designers and engineers to evaluate and compare the relative sustainability performance of different product. An evaluation model is established based on six dimension sustainability elements (Environment, Economy, Society, Functionality, Manufacturability, and Reusability) in order to provide a new comprehensive sustainability assessment framework in a closed-loop life cycle system. Furthermore, the multi-level hierarchical structure based on criteria and corresponding sub-criteria is utilized in order to conduct more effective analysis. The improved fuzzy multi-criteria decision method is employed incorporating subjective judgment and objective information to determine weights of criteria and related sub-criteria in real decision-making situation. The positive-ideal and negative-ideal solutions are employed to satisfy the designers’ desire to be as close as possible from the positive-ideal solutions. Sustainability performances of different manufactured products are assessed by integrating different levels sub-criteria into criteria. Illustrative example involving Bridgeport manual mill and Mori Seiki DuraVertical 5060 in three use environments is discussed to demonstrate the feasibility of the proposed methodology.

Improving mechanical properties of 13–93 bioactive glass robocast scaffold by poly (lactic acid) and poly (ε-caprolactone) melt infiltration

The effect of polymer infiltration on the mechanical properties of 13–93 bioactive glass scaffolds fabricated by robocasting has been investigated. Biodegradable polymers—poly (lactic acid) (PLA) and poly (ε-caprolactone) (PCL)—were infiltrated into selected robocast scaffolds by immersion of the structure in a polymer melt. The mechanical enhancement achieved upon impregnation on robocast 13-93 structures with fully-dense struts was found to be lower than in the currently existing literature due to the absence of microporosity. The modulus increase is negligible and the strengthening achieved is limited (<40% in the most favorable case of PLA impregnation under bending). However, the toughening produced by the polymer infiltrate, while lower than previously reported values in microporous structures, is still large (over one order of magnitude); especially when a ductile polymer infiltrate such as PCL is used. Indeed, the 13-93/PCL co-continuous composites were able to survive large strains with significant load-bearing capacity, even under bending stresses, or a rough, manual milling. On the other hand, the dense 13–93 frames fabricated by robocasting acted as good mechanical reinforcements for both polymers, with the exception of PLA under bending stresses.

Synthesis, microstructure and electromechanical properties of undoped (K0·5Na0·5)NbO3

Conventional solid state mixed oxide route using manual and ball milling is investigated for the preparation of K0·5Na0·5NbO3 (KNN) ceramics. Microstructure engineering was made using two milling methods and sintering techniques, and the crystal growth; then electromechanical properties were investigated as a function of sintering temperature, densification and grain size. The sintering conditions were set at 920°C/5 min for spark plasma sintering and 1090–1120°C/10 and 48 h for classical sintering. KNN crystal was grown using floating zone technique under nitrogen gas, where the translation and rotation speeds were fixed at 3 mm h−1 and 20 rev min−1 respectively. Piezoelectric and dielectric performances were measured and related to the microstructure. High kt (33 to 48%), kp of 18 to 48% and d33 of 127–140 pC N−1 were reached for relative densities of 84 to 96%. KNN ceramics are now available for the design of ultrasonic sensors.

Mechanochemical synthesis of Ni(OH)2 and the decomposition to NiO nanoparticles: Thermodynamic and optical spectra

Nickel hydroxide (Ni(OH)2) was prepared through a mechanochemical route using simple manual milling. NiO nanoparticles were obtained through subsequent calcinations. X-ray diffraction (XRD), differential thermal analysis and thermal gravimetric (DTA/TG), transmission electronic microscopy (TEM), Fourier transforming infrared spectroscopy (FTIR) and ultraviolet to visible spectroscopy (UV–vis) were adopted to characterize the structural, morphological, and optical properties of the obtained NiO products. Intensive study to the DTA curves of the Ni(OH)2 precursor was conducted to understand the thermal behavior and derive the activation energy, for which the Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose methods were introduced and were applied respectively. The average activation energy required to de-composite the Ni(OH)2 precursor in ambient condition was 117.8kJ/mol, which determined that the decomposition is controlled by the chemical reaction. NiO with cubic shape was obtained. Size of the products increased from 8.3nm at 350°C to 43.4nm at 600°C. Carbonates were found to co-exist with the product, which were generated in the preparing procedures. Band gap energy of the NiO was in the range of 3.30±0.11eV, which have no obvious relationship with the preparing conditions.

Evaluation of marginal adaptation and traction resistance of zirconium crowns made up using two different techniques and cemented on pins with three types of cements

Objective: The aim was to assess marginal adaptation of zirconium crowns made up by manual milling (pantograph) and computerized (computer assisted designing/computer assisted machining [CAD/CAM]) before and after cementation; and the efficiency of 3 types of cements in retaining these crowns: Zinc phosphate, resin modified glass ionomer cement (RelyX Luting 2) and resin cement (RelyX U200). Materials and Methods: Out of 30 zirconium crowns, 15 were milled by the pantograph, and 15 by CAD/CAM. Each group was divided into 3 subgroups according to the cement used. Cementation was done over the analog universal pin 4.5 mm × 4 mm and submitted to mensuration of marginal interface of its four faces with stereoscopic magnifier (×20). Then, they were directed to a machine of universal test (EMIC), and submitted to an axial traction with speed of 0.5 mm/min until its displacement. Results: Before cementation, CAD/CAM crowns (47.60; 40.20; 43.40 μm) demonstrated a greater desadaptation comparing to pantograph crowns (28.20; 35.60; 30.40 μm). RelyX Luting 2 showed less marginal desadaptation postcementation on CAD/CAM crowns (53.80 μm ± 8.43 μm) and pantograph (39.80 μm ± 12.696 μm), when compared with zinc phosphate (62.00 μm ± 12.86; 45.20 μm ± 24.035) and to RelyX U200 (73.80 μm ± 44.49 μm; e 53.00 μm ± 10.817 μm). RelyX Luting 2 also obtained better efficiency on traction resistance (9.48 Kgf ± 2.49 Kgf; e 24.54 Kgf ± 6.73 Kgf), when compared to zinc phosphate (8.71 Kgf ± 4.00 Kgf; and 11.85 Kgf ± 3.15 Kgf) and RelyX U200 (8.08 Kgf ± 0.62 Kgf; and 14.78 Kgf ± 5.94 Kgf). Conclusions: Lower values on marginal discrepancy were found on pantograph crowns comparing to CAD/CAM crowns. RelyX Luting 2 obtained not only a lower marginal desadaptation, but also a better efficiency on traction resistance among the three cements. However, there was no significant statistical difference that could prove the influence of desadaptation on displacement resistance.