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Hardness and Wear Resistance of Ni-B Alloy Coatings
No full textNi-B alloy coatings were prepared on copper substrate by constant current electroplating method from the electrolyte system with nickel sulfamate as main salt and sodium borohydride as boron source,and pure Ni coating and Ni-Fe alloy coating were prepared using similar method as control samples.Ni-B alloy coatings were heat treated in vacuum annealing furnace.The crystal structure and surface morphology were characterized by X-ray diffractometer and scanning electron microscopy,and the hardness and wear resistance were tested by microhardness tester and friction wear testing machine.Wear cracks morphology of the coatings were observed,and then the wear mechanisms were analyzed.Results showed that Ni-B alloy coatings featuring bright and smooth surface,the hardness reach up to 7000~8000 MPa. Furthermore,higher hardness value of about 11 000MPa can be obtained after heat treatment at 300℃.Compared to pure Ni coating and Ni-Fe alloy coating,Ni-B alloy coatings present better wear resistance
Wear resistance of electrodeposited Ni–B and Ni–B–Si3N4 composite coatings
No full textThe wear resistance of electrodeposited (ED) Ni–B and Ni–B–Si3N4 composite coatings is compared. The effect of incorporation of Si3N4 particles in the ED Ni–B matrix on the surface morphology, structural characteristics and microhardness has been evaluated to correlate the wear resistance. The wear mechanism of ED Ni–B and Ni–B–Si3N4 composite coatings appears to be similar; both involve intensive plastic deformation of the coating due to the ploughing action of the hard counter disc. However, the extent of wear damage is relatively small for ED Ni–B–Si3N4 composite coatings
electroless Ni-B-nanodiamond coating
Full text linkpeer reviewedThis report explores the effects of electroless Ni-B-nanodiamond plating bath parameters for optimization of the hardness and deposition rate based on response surface method (RSM). Quadratic models were developed and found to be mathematically appropriate for the optimization. The nanodiamonds (ND) and optimized coating were characterized using XPS, DLS, FIB-SEM, GDOES, microhardness, and nanoindentation. The results of the molecular dynamic simulation show low adsorption energy of borohydride on nanodiamonds surface is not favourable for borohydride dehydrogenation, therefore the boron content of the coating decreases when ND are added. Raman spectroscopy, SEM, and EDS analysis carried out on different zones of the surface after scratch test show nanodiamonds undergo graphitization and micro-cracking which block crack propagation at lower load. In addition, ND improves formation of the tribolayer at higher loads. The Raman spectroscopy results after indentation tests show the possibility of SP3 to SP2 phase transformation for nanodiamonds. The molecular dynamic simulation results confirm that phase transformation through monitoring the changes in nanodiamonds interatomic potential and interatomic distances. It is believed that the volume expansion caused by this phase transformation increases the toughness of coating
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Effect of electroless Ni-B, Ni-P/Ni-B VE Ni-B/Ni-P coatings on surface properties of AISI 316L stainless steel
Full text linkAISI 316L östenitik paslanmaz çelikler, birçok çözelti ortamında yüksek korozyon dirençleri nedeniyle farklı endüstriyel alanlarda yaygın olarak kullanılmaktadır. Ancak düşük sertlikleri ve düşük aşınma dirençleri endüstriyel uygulamalar için dezavantajlı özellikleridir. Geleneksel nitrürleme ve ısıl işlem prosesleri ile sertlik ve aşınma direnci özellikleri iyileştirilmesine rağmen çözelti ortamlarında klorür iyonu saldırısından çok hızlı etkilenmeleri nedeniyle genellikle korozyon dirençleri azalmaktadır. Akımsız nikel alaşım kaplamaların sert, aşınmaya ve korozyona dirençli bir yüzey sağladığı bilinmektedir. Bu yüzden mevcut çalışmada, tek tabakalı Ni-B ve dubleks Ni-P/Ni-B ve Ni-B/Ni-P ile kaplanmış 316L’nin kuru ve %0,9 NaCl çözelti ortamlarında aşınma, korozyon ve tribokorozyon davranışlarının, kaplanmamış 316L ile karşılaştırılarak incelemesi amaçlanmıştır. XRD analizi sonuçları ile kaplamaların kristal ve amorf yapı karışımına sahip olduğu belirlenmiştir. Optik mikroskop kesit görüntüleri kaplamaların ara yüzeylerinin homojen ve tabakalar arasında iyi bir uyum sağlandığını göstermiştir. Ni-B ve Ni-P/Ni-B kaplamaların en yüksek sertlik ve yüzey pürüzlülüğü değerleri gösterdikleri tespit edilmiştir. Yüksek sertliğinden dolayı Ni-B kaplama, 316L ve diğer dubleks kaplamalara kıyasla kuru ve korozif aşınma ortamlarında en düşük aşınma hacmi ve aşınma hızı değerlerine sahip olmuştur. Ni-B kaplamanın taramalı elektron mikroskobu görüntüleri ise plastik deformasyona karşı direnci artırdığı ve temas yüzeyleri arasındaki yapışmayı engellediğini göstermiştir. En yüksek korozyon potansiyeline sahip kaplama Ni-P/Ni-B olmasına rağmen Ni-B kaplama bu kaplamaya yakın korozyon özellikleri sergilemiştir. Tüm test sonuçları mekanik etkinin korozyondan daha baskın olduğunu göstermiştir. Bu yüzden mekanik (aşınma) ve kimyasal (korozyon) işlemlerin bir arada olduğu proseslerde 316L çelik için Ni-B kaplama kullanılması önerilmiştir.The AISI 316L austenitic stainless steels are widely used in different industrial areas due to its very high corrosion resistance in many aqueous environments. However, their low hardness and low wear resistance are disadvantageous properties for possible industrial applications. Conventional nitriding and heat treatment processes improves the low hardness and wear resistance, but generally decreases the corrosion resistance due to affected very quickly from attack of chloride ion in aqueous solution. Electroless nickel alloy coatings are known for providing a hard, wear and corrosion resistant surface. Thus, the present study aimed to investigate the wear, corrosion and tribocorrosion behaviours of single layer Ni-B and duplex Ni-P/Ni-B and Ni-B/Ni-P coated on 316L steel in comparison with untreated 316L steel in dry and 0,9 wt.% NaCl solution environments. It was determined that the coatings had a mixture of crystal and amorphous structures with the results of XRD analysis. OM observations of crosssection showed that the duplex interfaces on the 316L were uniform and the compatibility between the layers were good. The coatings reached the highest hardness and surface roughness values by deposition of the Ni-B and Ni-P/Ni-B coatings. Ni-B coating due to its high hardness had the lowest wear volume and wear rate values in dry and corrosive wear environments compared to untreated 316L and other duplex coatings. SEM images of the Ni-B coating showed that it increased the resistance to plastic deformation and prevented the adhesion between the contact surfaces. Although the Ni-P/Ni-B coating had the highest corrosion potential, the Ni-B coating exhibited similar corrosion properties with this coating. All test results showed that the mechanical effect was more dominant than corrosion effect. The use of Ni-B can be suggested instead of duplex coatings for 316L steel in synergistic combination of mechanical (wear) and chemical (corrosion) processes.Bilecik Şeyh Edebali Üniversites
MICROSTRUCTURE AND PROPERTIES OF THE Ni–B AND Ni–B–Ce ULTRASONIC-ASSISTED ELECTROLESS COATINGS
No full text We successfully obtained Ni–B and Ni–B–Ce coatings with and without sonication on low-carbon steel (Q235) through electroless plating with the deposition time of 60[Formula: see text]min. The surface morphology and elemental composition of the coatings were evaluated by scanning electron microscopy (SEM) and inductively coupled plasma (ICP). The 11[Formula: see text][Formula: see text]m thick sonicated Ni–B–Ce (Son-Ni–B–Ce) coating is uniform with the composition of Ni 87.1%, B 6.2% and Ce 6.6%. X-ray diffraction (XRD) measurements implied a typical broaden peak around 44∘, considered as amorphous structure which was confirmed by selected area electron diffraction pattern (SAED). Atomic force microscopy (AFM) showed a typical circular pit of Ni–B–Ce coating and Son-Ni–B–Ce coating. X-ray photoelectron spectroscopy (XPS) revealed the chemical status of coating components. The mechanical and corrosion resistance properties were determined by Vickers hardness tester, potentiodynamic polarization (Tafel) and electrochemical impedance spectroscopy (EIS) in 3.5[Formula: see text]wt. % NaCl solution. As a result, the Son-Ni–B–Ce coating revealed the optimum hardness (956[Formula: see text]HV), minimum roughness [Formula: see text] (92.38[Formula: see text]nm) and excellent corrosion resistance (3.65[Formula: see text][Formula: see text]Acm[Formula: see text] among all coatings. </jats:p
Ni-B and Ni-B-Zr catalyzed hydrogen production from mixtures of sodium borohydride and ammonia borane
No full textBu tez çalışmasında sodyum borhidrür, amonyak boran ve bunların birbirlerine göre çeşitli oranlardaki karışımlarının katalitik hidrolizi gerçekleştirilmiştir. Deneyler 25℃, 35℃ ve 45℃ olmak üzere 3 farklı sıcaklıkta ve saf NaBH4; saf NH3BH3; NaBH4/NH3BH3 oranı 2, 4 ve 8 olmak üzere beş farklı reaktif mol oranında yapılmıştır. Katalizör olarak in situ olarak sentezlenen Ni-B ve Ni-B-Zr tercih edilmiştir, katalizör hazırlama ve hidroliz reaksiyonları aynı reaktörde arka arkaya gerçekleşmiştir. Ni-B-Zr katalizörün daha iyi sonuçlar verdiği ve verimi arttırdığı görülmüştür. Ni-B-Zr katalizör ile yapılan deneyler kendi aralarında kıyaslandığı zaman, en iyi verim sonuçları 45℃ sıcaklıkta, saf NaBH4, NaBH4/NH3BH3 mol oranı 4 ve NaBH4/NH3BH3 mol oranı 8'de, sırasıyla %87, %86 ve %83 olarak görülmüştür. Ni-B-Zr katalizörü yardımıyla gerçekleşen hidroliz reaksiyonlarının reaksiyon kinetiği incelenerek NaBH4'ün ve NH3BH3'ün aktivasyon enerjileri sırasıyla 45.23 kJ/mol 79.76 kJ/mol olarak bulunmuştur. Son olarak, Ni-B ve Ni-B-Zr katalizörlerin SEM, BET, XPS analizleri yapılmıştır. NaBH4 kullanılarak sentezlenen Ni-B-Zr in situ katalizörlerin BET yüzey alanları, Ni-B in situ katalizörlerinki ile kıyaslandığında, Zr ilavesinin katalizörün yüzey alanı üzerinde çok büyük bir artış etkisi sağladığı gözlenmiştir. Katalizörün yüzey alanı 62 m²/g'dan 247.60 m²/g'a çıkmıştır.
In this study, catalytic hydrolysis of sodium borohydride, ammonia borane and their mixtures in different ratios was carried out. Experiments were carried out at 3 different temperatures (25 ℃, 35 ℃, 45 ℃) and in five different reactant molar ratios (pure NaBH4, pure NH3BH3, NaBH4/NH3BH3 ratio 2, 4, 8). As catalyst, in situ synthesized Ni-B and Ni-B-Zr were used. Catalyst preparation and hydrolysis reactions took place in the same reactor consecutively. It has been determined that Ni-B-Zr catalyst gives better results and increases efficiency. Experiments with Ni-B-Zr catalyst were compared, the best yield results were observed at 45 ℃ temperature, for pure NaBH4, for NaBH4/NH3BH3 mole ratio 4 and for NaBH4/NH3BH3 mole ratio 8, as 87%, 86% and 83%, respectively. By analyzing the reaction kinetics of hydrolysis reactions with Ni-B-Zr catalyst, activation energies of NaBH4 and NH3BH3 are calculated as 45.23 kJ/mol and 79.76 kJ/mol, respectively. Finally, SEM, BET, XPS analyzes of Ni-B and Ni-B-Zr catalysts were done. The BET surface area of Ni-B-Zr in situ catalyst which synthesized using NaBH4 was compared to that of Ni-B in situ catalyst, and it was obtained that the addition of Zr provided an enormous increase effect on the surface area of the catalyst. The surface area of the catalyst increased from 62 m²/g to 247.60 m²/g
Mechanical and Tribological Properties of Ni-B and Ni-B-W Coatings Prepared by Electroless Plating
No full textNi-B binary coating and Ni-B-W ternary coating were successfully prepared on titanium alloy (TC4) substrates by electroless plating to improve the hardness and wear resistance, followed by annealing treatment for better mechanical properties and tribological properties. The morphology, composition, microstructure, mechanical properties, and tribological behaviors of the coatings were characterized. Both as-plated coatings were amorphous, while the composition and morphology of the Ni-B-W coating differed from those of the Ni-B coating. Additionally, the Ni-B-W coating had better mechanical and tribological properties with a more considerable hardness (13.5 GPa), a minor friction coefficient (0.42), and a lower wear rate (0.10 × 10−7 cm3/(N·m)). After annealing, both coatings were crystalline. In parallel to the as-plated coating, the annealed coatings showed larger hardness values because of the formation of hard phases. Moreover, the crystalline grain of the coatings grew as the annealing temperature rose from 350 °C to 650 °C. Accordingly, the coatings showed a minor hardness value, a major friction coefficient, and severe wear under the same conditions. Above all, the Ni-B-W coating annealed at 350 °C showed the best performance, with an average grain size of 26.3 nm, hardness of 15.9 GPa, friction coefficient of 0.34, and wear rate of 0.09 × 10−7 cm3/(N·m)
Characterization and thermodynamic study of ultra-fine particle of Ni-B amorphous alloy
No full textUltra-fine particle of Ni-B amorphous alloy was prepared by chemical reduction of Ni2+ with NaBH4 and characterized with TEM and XRD. The heat capacity and thermal stability were measured with a high-precision automatic adiabatic calorimeter and DTA. The upper limit of applied temperature of the substance was found to be 684 K for use as catalyst. (C) 1999 Elsevier Science B.V. All rights reserved
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