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1
Li, Chong Jian, i Wen Peng. "Effect of Collocation Ratio of Coarse and Fine WC on Dual Grain Structure Cemented Carbide". Advanced Materials Research 154-155 (październik 2010): 1040–52. http://dx.doi.org/10.4028/www.scientific.net/amr.154-155.1040.
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This paper adopts area conversion method to measure the WC grain size manually, sets up a Fibonacci Sequence plane segmentation model based on the statistical data obtained, and studies the effect of the ratio of coarse WC grains to fine WC grains on dual grain structure cemented carbide. It is believed that when SWC (fine) / SWC (coarse) ratio is 0.382, theoretically speaking, the arrangement between WC grains is the tightest. Through investigating the effect of WC grain boundary fusion on its stacking density and contiguity, and the effect of the dissolution and precipitation of WC grains on SWC(fine) / SWC(coarse) ratio, and combining Li Guangyu’s random stacking structure of the cemented carbide theory, it expounds the formation mechanism of the dual grain structure cemented carbide—making a proper amount of fine WC grains fill in the gaps between coarse WC grains so as to increase the stacking density and contiguity of WC grains to the maximum degree, and to separate the accumulated Co-phase layer between coarse WC grains, so that the Co layer more evenly distributes among the fine WC grains.
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Cao, Jing, Fangyi Liu, Siyang Huang, Hong Liu, Zhigang Song, Jianyun Li i Guoshou Liu. "Effect of UFC on the Microscopic Pore Structure of Cemented Soil in Humic Acid Environment". Sustainability 15, nr 4 (10.02.2023): 3241. http://dx.doi.org/10.3390/su15043241.
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Peat soil is widely distributed in the Dianchi Lake area of Yunnan, and the effect of the cement deep-mixing method on peat soil foundation is mainly affected by humic acid (HA). In this paper, a composite cement curing agent is formed by adding different proportions of ultra-fine cement (UFC) to ordinary Portland cement (OPC) and used to cure the HA-containing cohesive soil. Mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and X-ray powder diffraction (XRD) are used to study the influence mechanism of UFC on the micropore structure of HA-containing cemented soil. The unconfined compressive strength test (UCS) is used to verify it. MIP, SEM, and XRD results show that UFC can significantly improve the microscopic pore structure of the samples. The hydration reaction rate of cement increases with the increase in the proportion of UFC, and the generated hydration products can fill the pores of the samples. The filling effect of hydration products on macropores is enhanced, and the pores change from fibrous filling to cemented filling. The enhanced cementation of the hydration products improved the loose and overhead structure inside the sample. Enhancing the cementation of hydration products improves the loose and overhead structure inside the sample and the integrity of cemented soil. UCS verified that the increase in the UFC proportion increases the HA-containing cemented soil strength. It achieves the purpose of reducing the amount of cement when curing peat soil foundations and supports reducing carbon emissions in practical projects.
3
Zhao, Kang, Qiang Li, Yajing Yan, Keping Zhou, Shuijie Gu i Shengtang Zhu. "Numerical Calculation Analysis of the Structural Stability of Cemented Fill under Different Cement-Sand Ratios and Concentration Conditions". Advances in Civil Engineering 2018 (27.08.2018): 1–9. http://dx.doi.org/10.1155/2018/1260787.
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The effect of lime-sand ratio and slurry concentration on the mechanical properties of backfills is important. To achieve green and high-efficiency mining, accurately determining the optimum ratio of cemented tailings for certain tungsten tailings and ensuring the safety and stability of the mine stope structure are important. The cement-sand ratios used in this research were 1 : 6 and 1 : 8. The mechanical properties were evaluated by using 68%, 72%, and 78% of tailing cemented filling materials. The corresponding physical and mechanical parameters were obtained through uniaxial compression, splitting, and shearing mechanical experiments on the backfill specimens. FLAC3D was used to investigate the mechanical properties of cement-filled pillars and the stability of supporting surrounding rocks on the basis of the mine’s current room pillar structure size parameters and mining sequence. The key factors that affect the stability of the goaf were analyzed by evaluating the plastic zone area of the stope, maximum and minimum principal stresses, and displacement change. The structural characteristics of stope structures and changes of rock mass damage were obtained under different cement-tailing ratios and concentrations. A cemented backfill with a cement-tailing ratio of 1 : 8 and a concentration of 68% was selected as the best solution for the mine in terms of safety and economic considerations.
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Liu, Naifei, Liang Cui i Yan Wang. "Analytical Assessment of Internal Stress in Cemented Paste Backfill". Advances in Materials Science and Engineering 2020 (22.12.2020): 1–13. http://dx.doi.org/10.1155/2020/6666548.
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To analytically describe the internal stress in a fill mass made of granular man-made material (cemented paste backfill, CPB), a new 3D effective stress model is developed. The developed model integrates Bishop effective stress principle, water retention relationship, and arching effect. All model parameters are determined from measurable experimental data. The uncertainties of the model parameters are examined by sensitivity analysis. A series of model application is conducted to investigate the effects of field conditions on the internal stress in CPB. The obtained results show that the proposed model is able to capture the influence of operation time, stope geometry, and rock/CPB interface properties on the effective stress in CPB. Hence, the developed model can be used as a useful tool for the optimal design of CPB structure.
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Béket Dalcé, Jean, Li Li i Pengyu Yang. "Experimental Study of Uniaxial Compressive Strength (UCS) Distribution of Hydraulic Backfill Associated with Segregation". Minerals 9, nr 3 (28.02.2019): 147. http://dx.doi.org/10.3390/min9030147.
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Stope backfilling with mine wastes has become a common practice in underground mines worldwide. Despite the increasing popularity in paste and rock fills, hydraulic fill made of classified mill tailings or sands remains commonly used in many mines. When such a slurried material is placed in a mine stope, a phenomenon known as segregation can take place associated with the quick drainage and consolidation of the hydraulic fill, thereby leading to a heterogeneous fill mass. While numerous publications have focused on the alleviation of segregation, there are few studies on the characterization of the distribution of geotechnical properties within hydraulic fill due to segregation. It is particularly scarce to quantify the spatial variation of the segregation and the resulting geotechnical properties after a backfill is placed in an opening. There is also a gap to quantitatively describe the degree of segregation using an appropriate expression or definition. The aim of this study is to investigate the effect of the segregation on the spatial variation of the geotechnical properties of hydraulic fill. Laboratory tests were performed with the cemented hydraulic backfill prepared with columns of different heights. The experimental results indicate that the segregation takes place and the resulting physical and mechanical properties can vary throughout the columns for samples higher than twice of the standard size. These results also indicate that the mechanical properties of a hydraulic fill obtained in a laboratory following the current practice with standard samples may not be representative of the fill mass placed in mine stopes. Expressions are proposed to quantify the degree of segregation associated with the spatial variation of particle sizes of mine hydraulic backfill.
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Moris, Izabela Cristina Maurício, Juliana Elias de Oliveira, Adriana Cláudia Lapria Faria, Ricardo Faria Ribeiro i Renata Cristina Silveira Rodrigues. "In Vitro Fit and Cementation Resistance of Provisional Crowns for Single Implant-Supported Restorations". Brazilian Dental Journal 26, nr 5 (październik 2015): 468–73. http://dx.doi.org/10.1590/0103-6440201300289.
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Abstract: This study aimed to verify marginal fit and the effect of cement film thickness standardization on retention of provisional crowns made with prefabricated acrylic cylinders on abutments, using two temporary luting agents subjected or not to mechanical cycling. Provisional crowns were made from bis-acryl (Luxatemp Fluorescence) or methyl methacrylate (Duralay) resins on acrylic cylinders and marginal fit and cement film thickness were evaluated. For retention evaluation, crowns were cemented with two temporary luting agents: non-eugenol zinc oxide (Tempbond NE) or calcium hydroxide-based (Hydcal) cements and subjected to tensile strength in a universal testing machine. After cleaning, debonded crowns were cemented again, subjected to mechanical cycling and retention was reassessed. The results of marginal fit and cement film thickness were analyzed by Student's t-test while retention of cements before and after mechanical cycling was analyzed using a mixed linear model. Methyl methacrylate crowns presented greater marginal misfit (p=0.001) and occlusal cement film thickness (p=0.003) than the bis-acryl ones. No difference was observed at axial cement film thickness (p=0.606). Resins (p=0.281) did not affect crown retention, but luting agents (p=0.029) and mechanical cycling (p=0.027) showed significant effects. The only significant interaction was mechanical cycling*luting agents, which means that luting agents were differently affected by mechanical cycling (p=0.002). In conclusion, the results showed that bis-acryl resin associated to calcium-hydroxide luting agent provided the best retention and lower cement thickness.
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Jia, Xiao Ming, Yue Xin Song i Suo Xia Hou. "Inhibition Effect of Compound Boricacidester on the Tungsten Carbide Leaching of the Cemented Carbide Tool". Advanced Materials Research 418-420 (grudzień 2011): 977–81. http://dx.doi.org/10.4028/www.scientific.net/amr.418-420.977.
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Working fluid is commonly used in the making and using progress of cemented carbide tool. The tungsten carbide leaching of cemented carbide tool will be resulted in by the sodium carbonate in cutting fluid, because of the tungsten carbide will occur oxidative dissolution. The inhibitor that suppress tungsten carbide leaching of cemented carbide tool is investigated by soaking experiments, friction experiments, SEM analysis, and energy spectrum analysis. The test result shows that aqueous solution and sodium carbonate will cause tungsten carbide leaching through oxidative dissolution; but compound boricacidester contain benzotriazole could suppress tungsten carbide leaching. The Inhibition mechanism is that compound boricacidester contain benzotriazole could generate complete and compact protective film on the surface of cemented carbide tool, therefore, tungsten carbide leaching is inhibited. Add compound boricacidester contain benzotriazole to the water-based cutting fluid could suppress tungsten carbide leaching effectively.
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Yuan, Jia Jing, Wen Zhuang Lu, Dun Wen Zuo i Feng Xu. "Contact Stress Analysis of NCD Coating on Cemented Carbide". Key Engineering Materials 431-432 (marzec 2010): 98–101. http://dx.doi.org/10.4028/www.scientific.net/kem.431-432.98.
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The contact stress of cemented carbide with NCD coating in elastic contact was analyzed using ANSYS. Factors such as elastic modulus and thickness of NCD film and elastic modulus of interlayer which affect the shear stress distribution of NCD film on cemented carbide substrate were investigated. The results show that the maximum shear stress point moves towards the interface with the increase of film elastic modulus. Film thickness has a significant effect on shear stress distribution of NCD film. High shear stress develops in the film layer with the increase of film thickness. Interlayer with low elastic modulus will cause shear stress concentration in NCD film.
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Jia, Xiao Ming, i Fei Wang. "Influence of Antirusting Aggent on the Cobalt Leaching of the Cemented Carbide Tool". Key Engineering Materials 407-408 (luty 2009): 317–20. http://dx.doi.org/10.4028/www.scientific.net/kem.407-408.317.
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The cutting fluid is widely used in cutting process with the cemented carbide tool. This paper studied the influence of some antirusting aggents, such as triethanolamine, tri-sodium phosphate, benzotriazole, sodium carbonate anhydrous, on the cobalt leaching of the cemented carbide tool by soaking test. The test results showed that a cobalt on cememted carbide surface and triethanolamine can produce complex compound into solution that made the cobalt leaching. The cobalt of the cemented carbide with the ion of the tri-Sodium phosphate in a water solution can form the loose deposition which leaded to the cobalt leaching.The benzotriazole and the cobalt can generate complex compound film covering on cemented carbide to effective inhibits the cobalt leaching. The inhibitive effect about the cobalt leaching of the sodium carbonate anhydrous is carried out through cathode reaction. The cobalt leaching of cemented carbide tool is effective inhibited by adding the benzotriazole and the carbonate anhydrous in the water-based cutting fluid.
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Gao, Bo, Shuai Cao i Erol Yilmaz. "Effect of Content and Length of Polypropylene Fibers on Strength and Microstructure of Cementitious Tailings-Waste Rock Fill". Minerals 13, nr 2 (18.01.2023): 142. http://dx.doi.org/10.3390/min13020142.
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The mechanical strength properties of cemented tailings backfill are very important for the safe and environmentally friendly mining of mineral resources. To check the impact of polypropylene fiber on strength and microstructure of cementitious tailings waste rock fill (CTWRF), diverse fiber lengths (6 and 12 mm) and dosages (0-control specimen, 0.3, 0.6, and 0.9 wt.%) were considered to prepare fiber-reinforced CTWRF (FRCTWRF) matrices. Experiments such as UCS (uniaxial compressive strength), X-ray CT (computed tomography), and SEM (scanning electron microscopy) were implemented to better characterize the backfills studied. Results showed that UCS performance of FRCTWRF was the highest (0.93 MPa) value at 6 mm fiber long and 0.6 wt.% fiber content. The peak strain of FRCTWRF was the highest (2.88%) at 12 mm fiber long and 0.3 wt.% fiber content. Growing the length of fiber within FRCTWRF can reduce its fracture volume, enhancing the crack resistance of FRCTWRF. Fiber and FRCTWRF are closely linked to each other by the products of cement hydration. The findings of this work will offer the efficient use of FRCTWRF in mining practice, presenting diverse perspectives for mine operators and owners, since this newly formed cementitious fill quickens the strengths required for stope backfilling.
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Chen, Wen Hua. "Study on Strength and Velocity of Longitudinal Wave of Low-Strength Concrete". Key Engineering Materials 302-303 (styczeń 2006): 451–56. http://dx.doi.org/10.4028/www.scientific.net/kem.302-303.451.
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A new kind of low-strength concrete is suggested to fill big caves to protect environment and ecosystem. The low-strength concrete have been studied regarding strength, wave propagation, water content, porosity, composition and cemented material by press experiments and sound wave analysis and shear tests. Those results show that: (1) the mechanical characteristics of low-strength concrete is complex; (2) strength of the low-strength concrete comes from interlocking of large-size crushed stones and bond of cement particle; (3) water content has significant effect (more than 30 percent) on velocity of longitudinal wave of the low-strength concrete and has little effect on strength; while effect of porosity of concrete on strength are more than 30 percent; (4) strength of low-strength concrete are controlled by both the content of crust stones and content of cement and a relationship of strength and velocity of longitudinal wave is proposed.
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Hai, Long, i Rongtao Bao. "Experimental Study on the Dip Angle Effect of Layered Cemented Fillers: A Sandblasting Treatment Applied to Mine Filling". Applied Sciences 13, nr 9 (23.04.2023): 5293. http://dx.doi.org/10.3390/app13095293.
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In order to study the effect of interlayer dip angle on the mechanical properties of tail sand cemented filler and to improve the deterioration of the mechanical properties of the filler caused by delamination, this study introduces the sandblasting method for treating the interface between old and new concretes in concrete science. Two types of delamination, natural delamination and sandblasting delamination, were produced for the tailing sand cemented filler specimens, and the interlayer dip angles were set to 0°, 10°, 20°, and 30°, respectively. Uniaxial compression tests were conducted at maintenance ages of 3 d, 7 d, 14 d, and 28 d, and damage models were established. The results show that (1) the uniaxial compressive strength and modulus of elasticity of the naturally delaminated specimens decrease and then increase with the increase of interlayer dip angle, and reach the lowest at the interlayer dip angle of about 20°. The uniaxial compressive strength and modulus of elasticity of sandblasted delaminated specimens with interlayer dip angle, not more than 20°, can bring positive gains in uniaxial compressive strength and modulus of elasticity, and the stable gains at high age can reach 6.4% and 39.7%, respectively. (2) The post-peak ductility of the two-layered types of specimens increases and then decreases with the increase of the dip angle between layers and reaches the optimum ductility at about 20° of dip angle. (3) The damage of the delaminated filling body is mainly in the form of tensile damage and conjugate shear damage, and the sandblasting treatment can improve the force transmission mode on the delamination surface. (4) Based on the damage evolution of the soil body with Weibull distribution, the damage instantiation model of the layered colluvial filler is constructed, which has high reliability for different interlayer dip angles. Accordingly, the findings of this study demonstrate that the addition of sandblasting can significantly reduce the degradation of the mechanical properties of the tailing sand cemented fill brought on by delamination at a slow dip angle (below 20°), and offer a helpful damage ontology model for use in engineering practice.
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Kraishan, G. M., i N. M. Lemon. "FAULT-RELATED CALCITE CEMENTATION: IMPLICATIONS FOR TIMING OF HYDROCARBON GENERATION AND MIGRATION AND SECONDARY POROSITY DEVELOPMENT, BARROW SUB BASIN, NORTHWEST SHELF". APPEA Journal 40, nr 1 (2000): 213. http://dx.doi.org/10.1071/aj99012.
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Calcite is a common authigenic mineral in subsurface sandstones of the Barrow Sub-basin, North West Shelf. It is present in several formations from different stratigraphic horizons, ranging from Permian to Cretaceous. It occurs as poikilotopic cement and fracture-fill particularly concentrated along one of the major listric faults in the eastern part of the sub-basin. A detailed petrographical and geochemical study was performed on the Early Cretaceous calcite cements in an attempt to provide information on their origin, distribution and effect on reservoir quality. Calcite cements are Ca-rich, Mg-poor with considerable amounts of Fe and are characterised by bright orange to yellow luminescent colours. The δ13C and δ180 values vary considerably, δ13C ranging from −2.0 to −23.5 %o PDB (average of −10.2 %o, ± 4.8 PDB), whilst δ180 values range from 19.3 to 25.4 SMOW (average of 21.1 %o, ± 1.8 SMOW). Calcite cements are characterised by elevated 87Sr/86Sr ratios with a range of 0.71029 to 0.71058 (average of 0.71043 ± 0.00012). The elemental and stable isotope compositions of the calcite cements indicate cementation from meteoric pore-waters, with the same source and timing of occurrence.Calcite cements formed in the mid-diagenetic history below 45°C. The carbon isotopic composition of calcite cements is interpreted to be sourced from bicarbonate and carbon dioxide generated by thermal decarboxylation of kerogen and oxidation of the early-generated oil. The model for calcite formation involves fluids rich in organic carbon having migrated up dip along faults to be trapped and mixed with meteoric-derived C02 to form pervasive calcite-cemented zones. These zones may reach up to 8 m thick and occlude the intergranular primary porosity. Subsequent tectonic reactivation and maturation of organic matter has resulted in late acidic water invasion to partially or completely dissolve the calcite cement to locally enhance reservoir quality.
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Xu, Huawei, Derek B. Apel, Jun Wang, Chong Wei i Yashar Pourrahimian. "Investigation of Backfilling Step Effects on Stope Stability". Mining 1, nr 2 (29.07.2021): 155–66. http://dx.doi.org/10.3390/mining1020010.
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Cemented rock fill (CRF) is commonly used in cut-and-fill stoping operations in underground mining. This allows for the maximum recovery of ore. Backfilling can improve stope stability in underground workings and then improve ground stability of the whole mine site. However, backfilling step scenarios vary from site to site. This paper presents the investigation of five different backfilling step scenarios and their impacts on the stability of stopes at four different mining levels. A comprehensive comparison of displacements, major principal stress, and Stress Concentration Factor (SCF) was conducted. The results show that different backfilling step scenarios have little influence on the final displacement for displacement in the stopes. Among the five backfilling scenarios, the major principal stress and stress concentration factor (SCF) have almost the same final results. The backfilling scenario SCN-1 is the optimum option among these five backfilling scenarios. It can immediately prevent the increase of the displacement and reduce the sidewall stress concentration, thereby preventing possible failures. Using the same strength of CRF can achieve the same effects among the four mining levels. Applying backfilling CRF of the same strength at different mining depths is acceptable and feasible to improve the stability of the stopes.
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Chen, Yi, Li Zhang, Zhiqiang Zhong i Shanlin Wang. "Effect of Substrates Characteristics on Tribological Behaviors of AlTiN-Based Coated WC–Co Cemented Carbides". Coatings 12, nr 10 (10.10.2022): 1517. http://dx.doi.org/10.3390/coatings12101517.
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The wear resistance of coated tools is a key technical parameter, which is indirectly affected by the substrate phase characteristics. WC–Co cemented carbides with varied WC grain sizes (0.4, 0.7, 1.2 μm) and Co contents (3, 6, 10, 12 wt.%) were used as the substrates. Single-layer Al0.52Ti0.48N and multilayer Ti0.89Si0.11N/TiAlSiN/Al0.52Ti0.48N films were deposited on the substrates by DC magnetron sputtering. Reciprocating friction tests were carried out in the air medium and the 3.5 wt.% NaCl aqueous solution, respectively. In the air medium, the films on the fine and the submicron WC–Co substrates with the weaker carrying capacity became worn through earlier than those on the ultrafine substrates. In the NaCl solution medium, for the ultrafine-grained WC–10Co substrates with different Co contents, the friction coefficients (FS) of the film had a linear negative correlation with the hardness (HS) of the substrates. With the decrease in the WC grain sizes or the Co contents, the wear rates of the coated alloys decreased gradually (by 19.7% and 34.5%, respectively). The regular patterns obtained can provide a reference for the selection and design of the phase composition of the cemented carbide substrates.
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Machry, RV, PE Fontana, TC Bohrer, LF Valandro i OB Kaizer. "Effect of Different Surface Treatments of Resin Relined Fiber Posts Cemented With Self-adhesive Resin Cement on Push-out and Microtensile Bond Strength Tests". Operative Dentistry 45, nr 4 (27.03.2020): E185—E195. http://dx.doi.org/10.2341/19-108-l.
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Clinical Relevance When luting relined fiber posts with self-adhesive cement, the surface treatment of the posts influences the adhesion of the fiber posts to root dentin. SUMMARY This study evaluated the effect of surface treatment and silanization of resin composite on the bond strength of relined fiber posts cemented with self-adhesive resin cement. Push-out and microtensile bond strength (MTBS) tests were performed in this study. The endodontic treatment of 80 single-rooted bovine teeth was first performed in the push- out test segment, followed by weakening the intracanal walls by diamond bur. Then, the glass fiber posts were adapted with resin composite to fill the root canals, followed by photoactivation and resin surface conditioning according to four different experimental conditions: no conditioning as control, 10% hydrofluoric acid, 35% hydrogen peroxide, or air abrasion with alumina particle (all groups were subdivided into “with silanization” or “without silanization,” thus totaling eight experimental groups). Self-adhesive resin cement was used for the post cementation. Four slices per tooth were obtained for the push-out tests. Next, 160 blocks of resin composite were first produced for the MTBS tests; their bonding surfaces were conditioned (as mentioned, ie, eight treatments), and they were cemented to each other. The 80 sets (n=10/treatment) were then cut into microbars (16/set): eight were immediately tested, while the other eight were thermocycled (12,000×) and stored (120 days) before MTBS. Failure modes and topographic analyses were performed after treatments. There was no statistically significant difference for the push-out results. In MTBS, surface treatment and silanization had a significant effect (p<0.001). Aging decreased bond strength for all groups. Considering the aged groups, air abrasion promoted the highest values and silanization improved bond strength for all treatments except air abrasion. The alumina particle air abrasion of the relining resin composite promoted the highest bond strengths when luting with self-adhesive resin cement.
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Song, Xinjiang, Haibo Xu, Deqin Zhou, Kai Yao, Feifei Tao, Ping Jiang i Wei Wang. "Mechanical Performance and Microscopic Mechanism of Coastal Cemented Soil Modified by Iron Tailings and Nano Silica". Crystals 11, nr 11 (31.10.2021): 1331. http://dx.doi.org/10.3390/cryst11111331.
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In order to explore the effect of composite materials on the mechanical properties of coastal cement soil, cement soil samples with different iron tailings and nano silica contents were prepared, and unconfined compression and scanning electron microscope tests were carried out. The results show that: (1) The compressive strength of cement soil containing a small amount of iron tailings is improved, and the optimum content of iron tailings is 20%. (2) Nano silica can significantly improve the mechanical properties of iron tailings and cement soil (TCS). When the content of nano silica is 0.5%, 1.5%, and 2.5%, the unconfined compressive strength of nano silica- and iron tailings-modified cement soil (STCS) is 24%, 137%, and 323% higher than TCS, respectively. (3) Nano silica can promote the hydration reaction of cement and promote the cement hydration products to adhere to clay particles to form a relatively stable structure. At the same time, nano silica can fill the pores in TCS and improve the compactness of STCS.
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Natascha Douat Hannegraf, Maria Eduarda Schultze Mendes Ribeiro, Célia Maria Condeixa de França Lopes i Flares Baratto-Filho. "Effect of heat on the hardness of glass carbomer cement used in atraumatic restorative treatment". RSBO 17, nr 1 (30.06.2020): 6–11. http://dx.doi.org/10.21726/rsbo.v17i1.273.
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This study aimed to evaluate the effect of heat treatment on the microhardness of two glass ionomer cements: EQUIA Forte (GC Corporation) and GCP Glass Fill (GCPDental). Material and methods: Twenty specimens of the two glass ionomer cements were prepared following the manufacturer’s instructions, and 10 specimens of each material received heat treatment with a light curing unit (Carbo LED lamp, GCP-Dental). After seven days of storage in distilled water at room temperature (23°C), the 40 specimens were submitted for Vickers microhardness test (microhardness HMV 2T). Five indentations were performed on each specimen with a load of 100g, with a 10 second penetration time. Results: For both materials, the average microhardness value were higher in the groups that did not undergo heat treatment, the group presenting with the highest microhardness value was EQUIA Forte (GC Corporation) without heat treatment (125.3), and the lowest value was found for GCP Glass Fill (GCP-Dental) with heat treatment (72.9). Conclusion: The heat treatment had no influence on the microhardness of the glass ionomer cements tested.
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Craig, Julie R. M., i Nicholas Dunne. "Biomechanics of Vertebroplasty: Effect of Cement Viscosity on Mechanical Behaviour". Key Engineering Materials 587 (listopad 2013): 416–21. http://dx.doi.org/10.4028/www.scientific.net/kem.587.416.
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Vertebroplasty is a minimally invasive surgical procedure, which requires efficacious percutaneous cement delivery via a cannulated needle to restore the strength and stiffness in osteoporotic vertebral bodies. Cement viscosity is understood to influence the injectability, cohesion and cement retention within the vertebral body. Altering the liquid to powder ratio modifies the viscosity of bone cement; however, the cement viscosity-response association between cement fill and augmentation of strength and stiffness is unknown. The aim of this study was to determine the relationship between viscosity, cement fill and the potential augmentation of strength and stiffness in an open pore foam structure that was representative of osteoporotic cancellous bone using an in vitro prophylactic vertebroplasty model. The results showed a strong linear correlation between compressive strength and stiffness augmentation with percentage cement fill, the extent of which was strongly dependent on the cement viscosity. Significant forces were required to ensure maximum delivery of the high viscosity cement using a proprietary screw-driven cement delivery technology. These forces could potentially exceed the normal human physical limit. Similar trends were observed when comparing the results from this study and previously reported cadaveric and animal based in vitro models.
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Mbonimpa, Mamert, Parrein Kwizera i Tikou Belem. "Mine Backfilling in the Permafrost, Part II: Effect of Declining Curing Temperature on the Short-Term Unconfined Compressive Strength of Cemented Paste Backfills". Minerals 9, nr 3 (11.03.2019): 172. http://dx.doi.org/10.3390/min9030172.
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When cemented paste backfill (CPB) is used to fill underground stopes opened in permafrost, depending on the distance from the permafrost wall, the curing temperature within the CPB matrix decreases progressively over time until equilibrium with the permafrost is reached (after several years). In this study, the influence of declining curing temperature (above freezing temperature) on the evolution of the unconfined compressive strength (UCS) of CPB over 28 days’ curing is investigated. CPB mixtures were prepared with a high early (HE) cement and a blend of 80% slag and 20% General Use cement (S-GU) at 5% and 3% contents and cured at room temperature in a humidity chamber and under decreasing temperatures in a temperature-controlled chamber. Results indicate that UCS is higher for CPB cured at room temperature than under declining temperatures. UCS increases progressively from the stope wall toward the inside of the CPB mass. Under declines in curing temperature, HE cement provides better short-term compressive strength than does S-GU binder. In addition, the gradual decline in temperature does not appear to affect the fact that the higher the binder proportion, the greater the strength development. Therefore, UCS is higher for samples prepared with 5% than 3% HE cement. Findings are discussed in terms of practical applications.
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Gunn, Elizabeth, Dinesh Gundapaneni i Tarun Goswami. "Effect of cement fill ratio in loosening of hip implants". Biomatter 2, nr 2 (kwiecień 2012): 87–93. http://dx.doi.org/10.4161/biom.20709.
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Porathur, J. L., S. Sekhar, A. K. Godugu i S. Bhargava. "Stability analysis of a free-standing backfill wall and a predictive equation for estimating the required strength of a backfill material - a numerical modelling approach". Journal of the Southern African Institute of Mining and Metallurgy 122, nr 5 (10.06.2022): 1–7. http://dx.doi.org/10.17159/2411-9717/1544/2022.
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Cemented backfilling has enabled underground hard rock mines to extract orebodies more safely with improved ore recovery. It is important to estimate the minimum required strength parameters for a backfill mix by optimizing the binder percentage to enable cost-effective and safe stoping operations. We conducted three-dimensional numerical modelling to study the effect of various stoping parameters on the stability of a free-standing backfill wall. A Mohr-Coulomb material model was used for the backfill material and the rock-fill interface. A strength reduction technique, excluding friction angle, was employed to arrive at a minimum stable strength value for the backfill. For a given combination of strength values, the stability state of the backfill wall could be demarcated using a displacement and yield zone tracking method. The numerical modelling results are compared to some earlier theoretical models. From the simulations, a predictive equation is developed to predict the required strength parameters for a backfill mix to ensure a stable free-standing wall. Examples are given of the successful use of the predictive equation at some underground hard rock mine sites in India.
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Yang, Baogui, Zhijun Zheng, Junyu Jin i Xiaolong Wang. "Time-Dependent Rheological Properties of Cemented Aeolian Sand-Fly Ash Backfill Vary with Particles Size and Plasticizer". Materials 16, nr 15 (27.07.2023): 5295. http://dx.doi.org/10.3390/ma16155295.
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The use of cemented Aeolian sand-fly ash backfill (CAFB) material to fill the mining area to improve the surface subsidence damage caused by underground coal mining is in the development stage. Their performance with large overflow water and strength loss is not well understood. Few research has been conducted to understand the effects of aeolian sand and coal gangue on the rheological properties of CAFB with plasticizers. Therefore, this study aims to investigate the effects of a plasticizer on the rheological properties, specifically yield stress and viscosity, of CAFB prepared with aeolian sand and coal gangue. CAFB mixes containing 0%, 0.05%, and 0.1% plasticizers were prepared, and yield stress and viscosity were determined at different intervals. Additional tests, such as thermal analysis and zeta potential analysis, were also conducted. It was found that the rheological properties of CAFB are the comprehensive manifestation of the composite characteristics of various models. Reasonable particle size distribution and less plasticizer can ensure the stability of the slurry structure and reduce the slurry settlement and the risk of pipe blocking. The findings of this study will be beneficial in the design and production of CAFB material.
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Jian, Xiao Gang, i Yun Hua Zhang. "Effect of Temperature on the Mechanical Property of the Film-Substrate Interface of Diamond Coatings". Applied Mechanics and Materials 670-671 (październik 2014): 506–11. http://dx.doi.org/10.4028/www.scientific.net/amm.670-671.506.
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Model of the film-substrate interface of diamond coatings is built with the method of molecular dynamic, and the molecular dynamic simulation is applied to study the mechanical property of the model based on the Morse potential function and Tersoff potential function with temperature ranging from 0K to 800K. The results show that the adhesive strength of the interface between the diamond coatings and the cemented carbide substrate behaves a downward trend when the temperature rises from 0K to 800K and the downward trend is sharp when the temperature increases from 0K to 300K and the downward trend is smooth when the temperature rises from 300K to 800K. Meanwhile, the varying trend of the energy with the temperature is similar to the adhesive strength.
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El Mkadmi, Nawfal, Michel Aubertin i Li Li. "Effect of drainage and sequential filling on the behavior of backfill in mine stopes". Canadian Geotechnical Journal 51, nr 1 (styczeń 2014): 1–15. http://dx.doi.org/10.1139/cgj-2012-0462.
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Underground backfilling offers significant economic and environmental advantages to mining operations. There is however a limited knowledge and understanding of how the backfill behaves within mine stopes, which creates some concern regarding the risk of accidents with potentially serious consequences. It is thus important to investigate further the response of backfill to ensure safe working conditions and optimize the filling sequence. This paper presents key results from a numerical study aimed at analyzing the hydrogeotechnical response of backfill in a narrow vertical stope. The simulations illustrate how stresses are influenced by stope geometry, water drainage, and filling rate. Three main cases are presented here to illustrate these effects; namely, (i) simulation of dry (or drained) backfill, (ii) a rapidly filled stope with progressive drainage and consolidation, and (iii) sequential backfill placement with different filling rates. The third case includes a simulation with evolving properties due to the binder added to the backfill. The results from the numerical analyses show that arching effects develop within narrow backfilled stopes because of the stiffness contrast between the rock and the fill material. This can produce a significant reduction of the stresses (horizontal and vertical) in comparison with the overburden pressure. The simulation results also show the development of excess pore-water pressures after the placement of the saturated backfill within the stope. Drainage tends to reduce these pressures and increase the frictional stresses along the rock walls. The sequentially filled stope simulations show that a rapid filling rate produces much higher total stresses and excess pore-water pressures, compared to slower rates. The simulation of the cemented backfill, with evolving properties, indicates that the progressive changes can have a significant effect on the total and effective stresses in the stope. A discussion follows on the implications of these results.
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Bouzakis, Konstantinos D., Stefanos Gerardis, G. Katirtzoglou, S. Makrimallakis, G. Skordaris i K. Efstathiou. "Chip Length Effect on the Wear of Coated Cemented Carbide Inserts in Milling". Key Engineering Materials 438 (maj 2010): 49–56. http://dx.doi.org/10.4028/www.scientific.net/kem.438.49.
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The effect of the developed chip length on the coated tool’s cutting performance was investigated. Milling experiments at various cutting speeds and chip lengths were performed, which resulted to different tool wear developments. To explain these results, a FEM simulation of the cutting process was conducted and the related chip geometries were predicted and compared to the corresponding experimental ones. Based on these results, the Coulomb friction coefficient between chip and tool rake was appropriately adjusted to achieve a sufficient correlation between experimental and computational data. By additional FEM calculations, the mechanical and thermal loads of the cutting edge were estimated and insight was provided concerning the effect of chip length on coated tool stresses and film fatigue fracture. The obtained results revealed that the chip length reduction improves the cutting performance of coated tools and a significant increase of the removed material volume and material removal rate as well can be achieved.
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Liu, Xiaosheng, Weijun Wang, Hai Wu, Jiaren Chen, Xuan Zhang i Liming Zhang. "Experimental Study of the Mechanical Properties of a Flexible Grid Filling Body". Applied Sciences 13, nr 10 (9.05.2023): 5858. http://dx.doi.org/10.3390/app13105858.
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The fill mining method has become more widely used due to its advantages of a high resource recovery rate, reliability and safety, and reduced surface tailings storage. However, the mechanical properties of the cemented fillings in fill mining are similar to those of ultra-low strength plain concrete, and there are problems such as high brittleness, low bending and tensile strength, and sudden failure. Using a flexible grid as reinforcement material, uniaxial compression, tensile, and shear tests of a flexible grid filling body were carried out, and the results were compared with the mechanical properties of the filling body without the flexible grid. We drew the following main conclusions: the uniaxial compressive strength of the flexible grid filling body gradually increased with the decrease in the grid spacing (the increase in the grid density); the grid dimension had little effect on the uniaxial compressive strength of the flexible grid filling body. The uniaxial tensile strength and shear strength of the flexible grid filling body increased with the increase in the grid dimension; and they first increased and then decreased with the increase in the grid spacing, and there was an optimal grid spacing. From the perspective of the macroscopic failure mode, the flexible grid filling body specimen after the uniaxial compression test had a conjugate shear failure, forming a “dumbbell shape” with two large ends and a small middle. After the uniaxial tensile test, the macroscopic failure mode of the specimen was tensile failure. After the shear test, the macroscopic failure mode of the specimen was shear slip failure. It is proposed that the tensile strength, shear strength, cohesion, and internal friction angle strengthening coefficients of the flexible grid filling body with different dimensions and spacing are higher than the elastic modulus strengthening coefficients. The experimental results can provide a certain reference and guidance for mine filling.
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Huang, Lei, Jun Tang Yuan, Zhen Hua Wang i Bin Bin Yu. "Effect of the Temperature on Diamond-Like Carbon (DLC) Thin Film Based on LIS". Applied Mechanics and Materials 421 (wrzesień 2013): 212–16. http://dx.doi.org/10.4028/www.scientific.net/amm.421.212.
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Diamond-like carbon (DLC) thin films were deposited on YG6 cemented carbide by an anode-layer linear ion source (LIS). The effect of different temperatures (20°C, 80°C, 115°C and 150°C) on DLC thin films was investigatedby using atomic force microscope (AFM), scanning electron microscope (SEM) and Raman spectroscopy. It was found thatthe surface roughness of the film decreased at first and then increased with the increase of the temperature, and reached the trough at 80°C. The intensity ratio (ID/IG) and the adhesion of the film increased at first and then decreased, and both of them reached the peak at 80°C. When the temperature was 80°C, the surface roughness was 6.9nm, the intensity ratio (ID/IG) was1.91 and the critical failure load was 107.23N. The results show that the temperatures have a great effect on the surface morphology and mechanism properties of DLC thin films. Consequently, this paperfurther studied the effect mechanism of different temperatures on DLC thin films based on the experiment.
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Campaner, Larissa Mendes, Alana Barbosa Alves Pinto, Amir Mohidin Demachkia, Tarcísio José de Arruda Paes-Junior, Clóvis Pagani i Alexandre Luiz Souto Borges. "Influence of Cement Thickness on the Polymerization Shrinkage Stress of Adhesively Cemented Composite Inlays: Photoelastic and Finite Element Analysis". Oral 1, nr 2 (21.06.2021): 168–80. http://dx.doi.org/10.3390/oral1020017.
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The objective of this study was to analyze the effect of cement thickness on the strain and stresses resulting from the polymerization of resin cement using photoelasticity and Finite Element Analysis (FEA). For this study, twenty upper first premolars with inlay cavity preparation were constructed from photoelastic resin and restored with composite resin inlay. The samples were divided into two groups (n = 10) according to the film thickness of resin cement material. For Group 1, the film thickness was 100 μm; for Group 2, the film thickness was 400 μm. After polymerization of the cement, photoelastic analysis and finite element analysis (FEA) were performed. In the photoelastic analysis, Group 2 showed higher strain with the presence of second-order fringe even after 24 h. In Group 1, the formation of first order fringes was not observed, even after 24 h. In the FEA analysis, the greatest cusp deflection and tensile stress occurred in Group 2 (0.00026 mm and 0.305 MPa, respectively) due to the polymerization shrinkage in the lingual cusp compared to Group 1 (0.000107 mm and 0.210 MPa, respectively). It can be concluded that the thickness of the resin cement influences the cusp deflection, with the greater thickness of the cement layer, the greater stresses and deformations in the tooth structure occur.
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Zheng, Kairui, Fazhan Yang, Na Zhang, Qingyu Liu i Fulin Jiang. "Study on the Cutting Performance of Micro Textured Tools on Cutting Ti-6Al-4V Titanium Alloy". Micromachines 11, nr 2 (25.01.2020): 137. http://dx.doi.org/10.3390/mi11020137.
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Titanium alloys are widely used in various fields, but their machinability is poor because the chip would easily adhere to the tool surface during cutting, causing poor surface quality and tool wear. To improve the cutting performance of titanium alloy Ti-6Al-4V, experiments were conducted to investigate the effect of micro textured tool on the cutting performances. The cemented carbide tools whose rake faces were machined with line, rhombic, and sinusoidal groove textures with 10% area occupancy rates were adopted as the cutting tools. The effects of cutting depth and cutting speed on feed force and main cutting force were discussed based on experimental results. The results show that the cutting force produced by textured tools is less than that produced by non-textured tools. Under different cutting parameters, the best cutting performance can be obtained by using sinusoidal textured tools among the four types of tools. The wear of micro textured tools is significantly lower than that of non-textured tools, due to a continuous lubrication film between the chip and the rake face of the tool that can be produced because the micro texture can store and replenish lubricant. The surface roughness obtained using the textured tool is better than that using the non-textured tool. The surface roughness Ra can be reduced by 35.89% when using sinusoidal textured tools. This study is helpful for further improving the cutting performance of cemented carbide tools on titanium alloy and prolonging tool life.
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Li, Faxin, Dawei Yin, Chun Zhu, Feng Wang, Ning Jiang i Zhen Zhang. "Effects of Kaolin Addition on Mechanical Properties for Cemented Coal Gangue-Fly Ash Backfill under Uniaxial Loading". Energies 14, nr 12 (21.06.2021): 3693. http://dx.doi.org/10.3390/en14123693.
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In this investigation, six groups of cemented coal gangue-fly ash backfill (CGFB) samples with varying amounts of kaolin (0, 10, 20, 30, 40, and 50%) instead of cement are prepared, and their mechanical properties are analyzed using uniaxial compression, acoustic emission, scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The uniaxial compressive strength, peak strain, and elastic modulus of CGFB samples decreased with the kaolin content. The average uniaxial compressive strength, elastic modulus, and peak strain of CGFB samples with 10% amount of kaolin are close to that of CGFB samples with no kaolin. The contribution of kaolin hydration to the strength of CGFB sample is lower than that of cement hydration, and the hydration products such as ettringite and calcium-silicate-hydrate gel decrease, thereby reducing strength, which mainly plays a role in filling pores. The contents of kaolin affect the failure characteristics of CGFB samples, which show tensile failure accompanied by local shear failure, and the failure degree increases with the kaolin content. The porosity of the fracture surface shows a decreasing trend as a whole. When the amount of kaolin instead of cement is 10%, the mechanical properties of CGFB samples are slightly different from those of CGFB samples without kaolin, and CGFB can meet the demand of filling strength. The research results provide a theoretical basis for the application of kaolin admixture in fill mining.
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Prakki, Anuradha, Renato Cilli, Alcides U. Da Costa, Sergio E. De Paiva Gonçalves, Rafael F. Lia Mondelli i Jose C. Pereira. "Effect of Resin Luting Film Thickness on Fracture Resistance of a Ceramic Cemented to Dentin". Journal of Prosthodontics 16, nr 3 (maj 2007): 172–78. http://dx.doi.org/10.1111/j.1532-849x.2006.00168.x.
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Ni, Zhuo, Xue Xiao Du, Shuai Wang, Feng Xing i Zhan Huang. "Effect of UF/Epoxy Microcapsules on Cement Composite". Advanced Materials Research 443-444 (styczeń 2012): 700–704. http://dx.doi.org/10.4028/www.scientific.net/amr.443-444.700.
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Effect of microcapsules on cement composites has been studied. The hydration of cement composite using microcapsules is studied by XRD and thermal techniques, showing that the addition of microcapsules has little affect on the hydration of cement. The pore size distribution and surface area of the cement composite with microcapsule are analyzed, showing a reduction in the pore content of cement composite and makes the pores smaller, which would improve durability and impermeability for designed materials. Damaging on cement and composites containing microcapsules and self-healing of these damagings can be reflected by the changes in their bending strength. When the cracks were generated in the composite, the microcapsules can release adhesive to fill in the space between the crackings, preventing cracking further growth.
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Skordaris, Georgios, Konstantinos Dionysios Bouzakis, Fani Stergioudi, Stefanos Kouparanis, Apostolos Boumpakis i Antonios Bouzakis. "Wear and Fatigue Behavior of PVD and MTCVD TiCN Coated Cemented Carbide Inserts in Turning Cast Iron". Defect and Diffusion Forum 404 (październik 2020): 101–8. http://dx.doi.org/10.4028/www.scientific.net/ddf.404.101.
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TiCN coatings of the same chemical compositions were deposited on HW/K05-K20 cemented carbide inserts via physical (PVD) and medium temperature chemical vapor deposition (MTCVD) techniques. Nano-indentations coupled with appropriate FEM simulations were used for characterizing the film and substrate mechanical properties. Furthermore, uncoated cemented carbide substrates were annealed in vacuum at temperatures and durations corresponding to the related ones during the PVD and MTCVD process for recording the effect of the deposition temperature and duration on the substrate strength properties. Perpendicular and inclined impact tests at various loads were performed for checking the coating fatigue endurance and adhesion respectively. These material data were considered in FEM supported calculations for predicting the developed stress fields in the cutting edge during turning cast iron GG30 using the PVD and MTCVD TiCN coated inserts. According to the obtained result, both coatings possess the same stress-strain properties. Hereupon, the MTCVD coatings are characterized comparably to PVD ones by improved fatigue properties and adhesion strength. Although these properties contribute to an increased tool life in finishing turning, the significant reduction of the substrate strength properties, due to the elevated temperature during the MTCVD process, results in a premature coating failure and a consequent intensive wear evolution in roughing.
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Aleisa, Khalil, Syed Rashid Habib, Abdul Sadekh Ansari, Ragad Altayyar, Shahad Alharbi, Sultan Ali S. Alanazi i Khalid Tawfik Alduaiji. "Effect of Luting Cement Film Thickness on the Pull-Out Bond Strength of Endodontic Post Systems". Polymers 13, nr 18 (13.09.2021): 3082. http://dx.doi.org/10.3390/polym13183082.
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Optimal bond strength between the prefabricated post/dowel to the surrounding dentin is essential. The present study aimed to analyze and compare the effect of three different cement film thicknesses on the pull-out bond strength of three different prefabricated post systems. Extracted natural teeth (N = 90) with similar root dimensions were acquired. Teeth were mounted in resin blocks, endodontically treated, sectioned at cemento-enamel junction, divided into three groups (A: Parapost Fiber Lux plus; B: 3M ESPE Relyx fiber post; and C: Parapost XP), and stored. Uniform post spaces were prepared for the groups (A and C: Length = 8 mm, Width = 1.5 mm; B: Length = 8 mm, Width = 1.6 mm). Each group (N = 30) was further subdivided into three subgroups (n = 10) based on the size (4, 5, and 6) of the post and cemented with resin cement (MultiLink-N, Ivoclar Vivadent). After thermocycling, the specimens were subjected to a pull-out test using a universal testing machine, and tensile force was recorded (MPa). Digital microscopic evaluations were performed for modes of failure. ANOVA and Tukey-HSD tests were used for statistics. Significant differences were observed for each tested material (p = 0.000). The lowest and highest bond strength values were recorded for Group C (Titanium post) and Group A (000), respectively. Multiple comparisons showed significance (p < 0.05) among all the groups, except for space 1 and space 2 (p = 0.316) for Group A. Most of the failures occurred within the cement-dentin and post-cement interface (Adhesive failures, 73.5%). An increase in the luting cement film thickness results in the decrease in pull-out bond strength of prefabricated posts luted with resin cement, irrespective of the type/material/shape of the post. The serrated fiber posts showed the highest pull-out bond strength compared to the smooth surfaced fiber posts or serrated metal posts. Increased pull-out bond strengths were observed when appropriate post space was created with the same sized drill as the post size.
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Huang, Biao, Qiong Zhou i Er-geng Zhang. "Effect of Thickness on Tribological Behavior of Hydrogen Free Diamond-like Carbon Coating". Coatings 10, nr 3 (6.03.2020): 243. http://dx.doi.org/10.3390/coatings10030243.
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The effects of film thickness on the tribological behavior have been investigated for hydrogen-free diamond-like carbon coating in this paper. The film was deposited on cemented carbide substrate (YG10C) by applying a high power impulse magnetron sputtering (HiPIMS) technique. The reciprocating ball on the disc test was conducted on the film with different thicknesses from 0.66~1.26 μm against the ZrO2 ball. The friction coefficient and wear resistance of the coating with different thickness showed a unimodal change. Numerous defects were observed on the surface of the film with a thickness of 0.66 μm and the wear mechanism was mainly plow-grinding. Therefore, the steady-state friction coefficient reached the maximum value of 0.22. The coating with a thickness of 1.01 μm had a higher sp3 content and a smoother, dense surface. A graphite transfer layer with low shear strength was detected on the ZrO2 ball against the film with a thickness of 1.01 μm, which led to the reduction in friction, thus the steady-state friction coefficient reached the minimum value of 0.10. However, the internal stress of the film increased with increasing thickness due to the distortion of the bond angle of internal structure when the film was bombarded by high-energy particles. The peeling coating was observed under reciprocating sliding, which both played the role of plowing and boundary lubrication film. The steady-state friction coefficient was 0.14 with a coating thickness of 1.26 μm. As a result, the hydrogen-free diamond-like carbon coating with optimized thickness shows a smooth and compact surface, low internal stress, high sp3 content, and better tribological properties.
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Song, Wenlong, Shoujun Wang, Zixiang Xia i Xuan Zhang. "Effect of microhole-textures filled with graphite on tribological properties of WC/TiC/Co carbide tools". Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 233, nr 11 (kwiecień 2019): 1627–38. http://dx.doi.org/10.1177/1350650119841220.
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To expand the industrial application of cemented carbide, micro-EDM was utilized to machine microhole-textures on the carbide surface; graphite powder was burnished into the textured microholes. The tribological properties of the microhole-textured tool combined with graphite were investigated and compared with the conventional one by carrying out reciprocating sliding friction tests and dry machining tests. Results exhibited that the microhole-textured tool combined with graphite possessed a much lower friction coefficient than that of the conventional one in sliding tests. The cutting forces, average friction coefficient at the tool–chip interface, and rake face wear of the textured tool were reduced, and the workpiece surface quality was also slightly improved. The worn regions of carbide specimen were examined and studied, and the possible effect mechanisms for the enhancement of friction and wear properties mainly consisted of the formation of uneven graphite film by friction extrusion, reduction of actual contact length, entrapment of wear debris and supply of graphite lubricant.
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Xu, Zhenqing, Leonid Lev, Michael Lukitsch i Ashok Kumar. "Analysis of residual stresses in diamond coatings deposited on cemented tungsten carbide substrates". Journal of Materials Research 22, nr 4 (kwiecień 2007): 1012–17. http://dx.doi.org/10.1557/jmr.2007.0120.
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Residual stresses in diamond films grown on WC–Co substrates have been investigated by Raman spectroscopy, x-ray diffraction (XRD), and curvature methods. Microcrystalline diamond films were deposited at 650–700 °C in a conventional hydrogen–methane environment by the microwave plasma-enhanced chemical vapor deposition technique. The film thickness, measured from cross-sectional micrographs taken by scanning electron microscopy, changed from 1.5 to 16.5 μm as the growth time increased from 1 to 12 h. The type and the magnitude of the total residual stress obtained from curvature and XRD measurements agreed very well in all of the samples and changed from tensile to compressive as film thickness increased. However, Raman spectroscopy results showed that all films exhibited compressive stress due to the domain size effect. Different methane fractions, varying from 1% to 3%, have been utilized for diamond growth, and the total residual stress increased as more methane was included.
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Hsu, Sung Chi, Huan Yang Chiang i Ji Yuan Lin. "Effect of Gradation and Cement on the Properties of Soil-Cement Mixtures". Advanced Materials Research 535-537 (czerwiec 2012): 1719–22. http://dx.doi.org/10.4028/www.scientific.net/amr.535-537.1719.
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Eight non-plastic soils with different gradation are used for this research to study the appropriate choice of soil-cement mixture for a earth and rock-fill dam construction project. The properties of soil-cement materials are influenced by several factors, including type and proportion of soil, cementitious materials, water content, compaction, uniformity of mixing, curing conditions, and age of the compacted mixture. Based on the experimental results, the maximum dry density will increase with an increase in cement content for soils with low fines content. However, no significant variation was noticed for soils with higher fines content. For given cement content, the maximum density of soil-cement mixture also has a positive correlation with the average grain size, D50, and uniformity coefficient of gradation, Cu. Based on USBR criteria and experimental results, a minimum of 11% of cement content are suitable for soil-cement application on the dam construction. Coarser grain soils are more applicable than finer grain soils to soil-cement construction.
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Bouzakis, K. D., E. Bouzakis, S. Kombogiannis, R. Paraskevopoulou, G. Skordaris, S. Makrimallakis, G. Katirtzoglou i in. "Effect of silicon content on PVD film mechanical properties and cutting performance of coated cemented carbide inserts". Surface and Coatings Technology 237 (grudzień 2013): 379–89. http://dx.doi.org/10.1016/j.surfcoat.2013.06.044.
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Nguyen, KV, RH Wong, J. Palamara i MF Burrow. "The Effect of Resin-modified Glass-ionomer Cement Base and Bulk-fill Resin Composite on Cuspal Deformation". Operative Dentistry 41, nr 2 (1.03.2016): 208–18. http://dx.doi.org/10.2341/14-331-l.
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SUMMARY Objectives: This study investigated cuspal deformation in teeth restored with different types of adhesive materials with and without a base. Methods: Mesio-occluso-distal slot cavities of moderately large dimension were prepared on extracted maxillary premolars (n=24). Teeth were assigned to one of four groups and restored with either a sonic-activated bulk-fill resin composite (RC) (SonicFill), or a conventional nanohybrid RC (Herculite Ultra). The base materials used were a flowable nanofilled RC (Premise Flowable) and a high-viscosity resin-modified glass-ionomer cement (RMGIC) (Riva Light-Cure HV). Cuspal deflection was measured with two direct current differential transformers, each contacting a buccal and palatal cusp. Cuspal movements were recorded during and after restoration placement. Data for the buccal and palatal cusp deflections were combined to give the net cuspal deflection. Results: Data varied widely. All teeth experienced net inward cuspal movement. No statistically significant differences in cuspal deflection were found among the four test groups. Conclusions: The use of a flowable RC or an RMGIC in closed-laminate restorations produced the same degree of cuspal movement as restorations filled with only a conventional nanohybrid or bulk-fill RC.
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Ameen, S., i A. Dahi Taleghani. "Dynamic Modeling of Channel Formation During Fluid Injection Into Unconsolidated Formations". SPE Journal 20, nr 04 (20.08.2015): 689–700. http://dx.doi.org/10.2118/173891-pa.
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Summary Injectivity loss is a common problem in unconsolidated-sand formations. Injection of water into a poorly cemented granular medium may lead to internal erosion, and consequently formation of preferential flow paths within the medium because of channelization. Channelization in the porous medium might occur when fluid-induced stresses become locally larger than a critical threshold and small grains are dislodged and carried away; hence, porosity and permeability of the medium will evolve along the induced flow paths. Vice versa, flowback during shut-in might carry particles back to the well and cause sand accumulation inside the well, and subsequently loss of injectivity. In most cases, to maintain the injection rate, operators will increase injection pressure and pumping power. The increased injection pressure results in stress changes and possibly further changes in channel patterns around the wellbore. Experimental laboratory studies have confirmed the presence of the transition from uniform Darcy flow to a fingered-pattern flow. To predict these phenomena, a model is needed to fill this gap by predicting the formation of preferential flow paths and their evolution. A model based on the multiphase-volume-fraction concept is used to decompose porosity into mobile and immobile porosities where phases may change spatially, evolve over time, and lead to development of erosional channels depending on injection rates, viscosity, and rock properties. This model will account for both particle release and suspension deposition. By use of this model, a methodology is proposed to derive model parameters from routine injection tests by inverse analysis. The proposed model presents the characteristic behavior of unconsolidated formation during fluid injection and the possible effect of injection parameters on downhole-permeability evolution.
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Zhang, Hong, He Li, Qian Cong, Zhimin Zhang, Aobo Du i Ying Wang. "Effect of proximal box elevation on fracture resistance and microleakage of premolars restored with ceramic endocrowns". PLOS ONE 16, nr 5 (26.05.2021): e0252269. http://dx.doi.org/10.1371/journal.pone.0252269.
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Background Restoration of endodontically treated premolar is in high risk for biomechanical failure, and often presents with subgingival margins. Proximal box elevation (PBE) has been used to relocate subgingival cavity outlines. Objective To evaluate the influence of PBE on fracture resistance and gingival microleakage of premolars with endodontic access cavities following ceramic endocrown. Methods Eighty sound maxillary premolars with standardized Class II cavities on mesial surfaces were randomly assigned to four groups (n = 20 in each group). Groups E1, E2 and E3, with proximal margins located in dentin/cementum, 2 mm below the cemento-enamel junction (CEJ), simulated subgingival location. Group E4 (supragingival group), with proximal margins located in enamel, 1 mm above the CEJ, was used as the positive control. For margin elevation of the proximal cavities, bulk-fill Smart Dentin Replacement (SDR), a visible light cured resin composite, was applied in group E1, and conventional resin composite (3M Z350 XT, a light-activated composite) was placed in group E2. Group E3 was only treated with a ceramic crown and served as the negative control. In all groups, computer-aided design (CAD) ceramic endocrowns were adhesively inserted, and fracture resistance, failure mode and microleakage were evaluated. Results A higher fracture resistance value was observed in PBE groups E1 and E2, regardless of the materials used (P = 0.038, and 0.010, respectively, vs E3), and fracture resistance in group E1 was higher than that in group E2. In teeth without PBE, the percentage of catastrophic failures reached 70%. Compared to group E3, a lower frequency distribution of microleakage was detected in supragingival group E4 (P = 0.031). No increased percentage of microleakage was observed in groups treated with PBE. Conclusion For endodontically treated maxillary premolars restored with ceramic endocrowns, PBE increases fracture resistance but not microleakage.
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Wi, Kwangwoo, Han-Seung Lee, Seungmin Lim, Mohamed A. Ismail i Mohd Warid Hussin. "Effect of Using Micropalm Oil Fuel Ash as Partial Replacement of Cement on the Properties of Cement Mortar". Advances in Materials Science and Engineering 2018 (14.11.2018): 1–8. http://dx.doi.org/10.1155/2018/5164030.
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This study investigates the effects of micropalm oil fuel ash (mPOFA) on compressive strength and pore structure of cement mortar. Various experimental techniques, such as compression test, isothermal calorimetry, mercury intrusion porosimetry, and X-ray diffraction, are performed to figure out the effect of using mPOFA as partial replacement of cement on the hydration of cement and determine its optimal replacement level to increase mechanical property of the mortar specimens. 10 wt.% of cement replacement with mPOFA is found to give the highest level of compressive strength, achieving a 23% increase over the control specimens after 3 days of curing. High K2O contents in mPOFA stimulate C3S in cement to form C-S-H at early ages, and high surface area of mPOFA acts as a nucleus to develop C-S-H. Also, small mPOFA particles and C-S-H formed by pozzolanic reaction fill the pores and lead to reduction in large capillary pores. In XRD analysis, a decrease in Ca(OH)2 and SiO2 contents with age confirmed a high pozzolanic reactivity of mPOFA.
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A Lei, María, Ricardo L Macchi i Mariana Picca. "Effect of photopolymerization time on the microhardness of resin cement beneath feldspathic ceramic". Acta Odontológica Latinoamericana 36, nr 1 (29.04.2023): 40–46. http://dx.doi.org/10.54589/aol.36/1/40.
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During ceramic veneer luting, resin cement polymerization is performed with interposition of the dental ceramic. Aim: To evaluate how and how much the photoactivation time affects the Vickers hardness of resin-based cements with interposed ceramic. Materials and Method: A total 24 specimens 11 mm in diameter and 1 mm thick were made from Paracore White Coltene (PC), Densell Resin Duo Cement (DC), 3M RelyX Veneer (RX) and Coltene Fill Up! (FU), interposing Vitablock Mark II (Vita Zahnfabrik) feldspathic ceramic 0.6 mm thick during photoactivation. The materials were polymerized using 100% and 25% of the times indicated by the manufacturers with a Coltolux LED (Coltene) light with intensity 1200 mW/cm2 . Each polymerization time group consisted of three specimens of each material, which were stored dry in darkness at 37 °C for 7 days. Three Vickers microhardness measurements were made on the top and bottom surfaces of each specimen using a Vickers Future Tech FM300 microhardness tester (300 g, 5 s). The values were averaged, and the bottom/top ratios calculated. Results were analyzed by ANOVA. (p<0.05) complemented with multiple comparisons using Tukey’s test (p<0.05). Results: Different photoactivation times were found to have a significant effect on hardness values of the cements evaluated, with significant differences between some of the cements. No statistically significant difference was found for the effect of photoactivation time on bottom/top microhardness ratio in those materials. Conclusions: Under the experimental conditions employed, it can be concluded that photopolymerization for shorter times and the interposition of restorative material significantly affect polymerization quality as evaluated by microhardness, but the bottom/top ratio was unaffected by differences in polymerization time.
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Honda, Michiyo, Toshiisa Konishi, Minori Mizumoto i Mamoru Aizawa. "In Vitro Biological Evaluation of Anti-Tumor Effect of the Chelate-Setting Hydroxyapatite Cement". Key Engineering Materials 529-530 (listopad 2012): 173–77. http://dx.doi.org/10.4028/www.scientific.net/kem.529-530.173.
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Cancers frequently metastasize to bone, where it leads to secondary tumor growth, and osteolytic bone degradation. Bone metastases are often associated with fractures and severe pain resulting in decreased quality of life. Accordingly, effective therapies to inhibit the development or progression of bone metastases will have important clinical benefits. Bone cement, one of the powerful tools as bone substitutes, is used to fill the resection voids. The aim of this study was to develop a local drug delivery system using HAp cement as a carrier of chemotherapeutic agents. In the present study, we have fabricated chelate-setting apatite cements (IP6-HAp cements) using HAp particles surface-modified with inositol hexaphosphate (IP6) and evaluated their anti-tumor effect. Human osteosarcoma (HOS) cultured on IP6-HAp cements (over 3000 ppm IP6) resulted in inhibition of cell growth. DNA microarray analysis indicated changes in the expression of apoptosis-related genes on IP6-HAp cement surface-modified with 5000 ppm IP6 compared with HAp cement, suggesting activation of apoptosis machinery by IP6-HAp cement. To clarify the mechanism of anti-tumor effect of IP6-HAp cement, the properties of cement were investigated. The release kinetics of IP6 from IP6-HAp cement showed that the level of released IP6 was insufficient to induce anti-tumor activity. These results led us to consider that locally high concentration of IP6 which was released from cement acts on the cells directly as anti-tumor agent and induces the apoptosis. Consequently, IP6-HAp cement might gain the anti-tumor effect and act as a carrier for local drug delivery system.
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აწყვერელი ლ., Atskvereli L., Bregadze O. ბრეგაძე ო. i Chuchulashvili N. ჭუჭულაშვილი ნ. "NASAL BONE RECONSTRUCTION USING BONE CEMENT - “SURGICAL SIMPLEX P”". TSMU COLLECTION OF SCIENTIFIC WORKS 49 (11.04.2019): 8–10. http://dx.doi.org/10.52340/csw.v49i0.138.
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Surgical treatment of the defects and deformations in the facial area are still actual problems of reconstructive surgery. Medical and social aspects of the problem, pushes for intense search of the new materials for the reconstruction and improvement of surgical methods. The work presents an interesting clinical case description. The authors successfully used radiopaque medical cement “Surgical Simplex P” to fill in the deficit of the nasal bone and cartilage. It should be noted that the satisfactory effect was achieved in both functional and aesthetic point of view.
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LEI, X. L., Y. HE i F. H. SUN. "EFFECT OF DIAMOND INTERLAYER ON THE TRIBOLOGICAL PROPERTIES OF TiAlN FILM SLIDING AGAINST CARBON STEEL". Surface Review and Letters 25, nr 06 (sierpień 2018): 1950001. http://dx.doi.org/10.1142/s0218625x1950001x.
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In this study, the effect of diamond interlayer on the tribological properties of titanium aluminum nitride (TiAlN) film sliding against medium carbon steel is investigated in dry rotary friction tests, by evaluating the coefficients of friction (COFs), wear rates, worn surfaces and element transitions of the contacted surfaces in the cemented carbide (WC-Co)-steel, TiAlN-steel, microcrystalline diamond (MCD)-steel, TiAlN/MCD-steel, micro- and nano-crystalline diamond (MNCD)-steel and TiAlN/MNCD-steel contacting pairs. It is found that compared with the TiAlN monolayer, the TiAlN/MCD bilayer film shows 57% higher COF, while the COF of TiAlN/MNCD multilayer inversely drops as much as 54%, due to the distinguished surface diamond grain morphologies of the MCD and MNCD interlayers as well as the copied effect of the TiAlN layer with relatively small thickness. Meanwhile, the diamond interlayer can provide robust load support for the top TiAlN layer, induce the wear mechanism transform from the abrasive wear to adhesive wear, and result in the mild wear of TiAlN/MCD and TiAlN/MNCD multilayers compared to the TiAlN monolayer. Moreover, the softer TiAlN top layer on MCD and MNCD interlayers can effectively improve the storage capacity of element oxygen and worn steel ball debris as well as accelerating the surface chemical reactions to form a smoother continuous ionic metal oxides tribofilm in the contacted zones due to its good self-lubricating property. Among all the hard coatings discussed when sliding against medium carbon steel, the TiAlN/MNCD coating shows the lowest COF and mild wear, due to the robust load support capacity of the beneath MNCD layer as well as the good self-lubricated and tribofilm formation capacity of the top TiAlN layer, which shows broad application potential in carbon steel machining.
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Ma, Yu Ping, Ming Chen i Fang Hong Sun. "Study on the Optimization of Deposition Processing Technology of Diamond Coated Tools". Advanced Materials Research 69-70 (maj 2009): 16–19. http://dx.doi.org/10.4028/www.scientific.net/amr.69-70.16.
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Diamond films was deposited on cemented carbide tools with two-step pretreatment method under different distances between the substrates and hot filaments, and the effect of the distance between the substrates and hot filaments on the crystallographic orientation of diamond films and the characteristics of diamond coated tools was investigated in bias-enhanced HFCVD system in this paper. The cutting performance of diamond coated tools was verified by the experiments of cutting particles reinforced aluminum base composite material with 15 vol.% Si as compared with uncoated ones. The quality of diamond film was analyzed by means of Scanning Electron Microscopy(SEM), Raman spectroscopy, and X-ray diffraction. The optimization deposition processing was obtained. The relative intensity ratio of (111) facet and (220) facet in the film tested by XRD was one third. The cutting performance of diamond coated tool was improved significantly when machining the Si particle reinforced aluminum-based metal matrix composite; its lifetime was 30 times longer than that of uncoated one. The work done in this paper was of great practical significance to accelerate the industrialization of diamond films coated WC–Co substrates.
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Lei, Xuelin, Yun He i Fanghong Sun. "Tribological properties of TiN/diamond and TiAlN/diamond bilayer films sliding against carbon steel". Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 232, nr 8 (29.12.2017): 1014–24. http://dx.doi.org/10.1177/1350650117750975.
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In this study, the tribological properties of the monolayer micro-crystalline diamond and nano-crystalline diamond films, TiN/diamond and TiAlN/diamond bilayer films on cemented tungsten carbide substrates are evaluated by dry sliding against the medium carbon steel counterpart balls, in terms of the coefficient of friction, wear rate, worn surfaces, and chemical transitions in the contacting wear zones. The significant coefficient of friction reducing effect of top-layer TiN and TiAlN coating only happens on the nano-crystalline diamond film, where the stable coefficient of friction of TiN/nano-crystalline diamond or TiAlN/nano-crystalline diamond bilayer coating reduces 9% or 53% compared with the nano-crystalline diamond film. The formed ionic metal oxides such as Fe2O3 or Fe3O4 coming from the chemisorbing of the atmospheric molecular water, oxygen in the air and the delamination of steel ball due to the repeated friction interaction is supposed to be responsible for the coefficient decreasing effect. The TiN or TiAlN film on diamond layer exhibits lower positive wear rate compared with the TiN or TiAlN film itself, due to the load support ability improvement resulted from the high hardness of diamond interlayers. Among all the tested hard films, the TiAlN/nano-crystalline diamond bilayer coating exhibits the valid potential to be the optimized tool coating in carbon steel machining in terms of its low coefficient of friction and wear rate, which may come from the self-lubricated transfer tribolayer formation on the TiAlN layer, as well as the enhanced mechanical supporting capacity of the underneath smooth and hard nano-crystalline diamond interlayer.