Search

The present study aims to investigate the effect of reinforcing TiB2 particles on the properties of in situ synthesized Ti3SiC2. For this purpose, TiB2/Ti3SiC2 composites with 5, 10, and 15 wt%TiB2 addition were synthesized through spark plasma sintering. TiB2/Ti3SiC2 composites were fabricated by this technique for the first time and the effect of TiB2 addition was evaluated comprehensively in terms of sintering behavior and density, phase development, microstructure, mechanical, thermal, and wear properties. Fully densified TiB2/Ti3SiC2 composites without the formation of any impurity phases were obtained at 1300 °C, for 15 min, under a pressure of 50 MPa. The mechanical properties and thermal diffusivity of composites were increased with the increasing TiB2 content. The most significant effect of TiB2 addition was obtained in wear properties compared to Ti3SiC2 matrix.

SiAlON ceramics and their derivatives are potential materials for tribological applications where wear and friction are very crucial. TiN is a reinforcement phase and solid lubricant for SiAlON used to improve mechanical and tribological properties. In this study, αı:βı-SiAlON composites incorporating nano- and micron-size TiN particles were produced by a gas pressure sintering method. Tribological behavior of the composites was investigated based on reinforcement particle size and physico-mechanical properties. Tribology tests were performed with a computer-controlled tribometer under dry unlubricated conditions with ball-on-disk configuration. It was found that the TiN particle size has an effect on surface roughness and hence the coefficient of friction. When the TiN particle size decreased to nano size, the wear mechanism was tribochemical, whereas, when the particle size increased to micron size, severe mechanical wear was observed besides tribochemical wear.

This study presents the tribological behavior of epoxy matrix composites containing two different fillers. The composites contain fillers with different particle sizes (

URL:http://sujest.selcuk.edu.tr/sumbtd/article/view/534 DOI: 10.15317/Scitech.2018.115, This study evaluates the effect of employment of vacuum application on the mechanical and tribological properties of porcelain waste added epoxy matrix composites. Tribological characterization was determined by friction, wear rate and mechanisms using ball-on-disk test by tungsten carbide counter-part without lubrication at room temperature. It is investigated the role of vacuum application on the wear mechanisms, tribo-chemical layer formation on the wear surfaces, frictional property and tribological performance. The microstructure, mechanical and physical properties and wear behavior correlation were discussed comprehensively. Vacuum application provided fully embedded and well wetted particles, and strong bonding strength between matrix and filler. It is demonstrated that well bonded particle reinforced composites have higher wear resistance, by resulting lower friction coefficient, and more smoother tribochemical layer than compared with the unvacuumed composites., Bu çalışma, vakum uygulamasının atık porselen katkılı epoksi matrisli kompozit malzemelerin mekanik ve tribolojik özelliklerine etkisini değerlendirmektedir. Tribolojik karakterizasyon; tungsten karbür aşındırıcı bilye kullanılarak oda sıcaklığında yağlayıcı olmadan bilye-disk (ball-on-disk) konfigürasyonunda triboloji testleri gerçekleştirilerek sürtünme, aşınma oranları ve aşınma davranışları belirlenmiştir. Vakum uygulamasının; aşınma mekanizmaları, aşınma yüzeylerinde tribo-kimyasal tabaka oluşumu, sürtünme özellikleri ve tribolojik performans üzerindeki rolü araştırılmıştır. Mikroyapı, mekanik ve fiziksel özellikler ile aşınma davranışı ilişkisi ayrıntılı incelenmiştir. Vakum uygulaması partiküllerin daha iyi ıslatılmasına, matris ve partikül arasında daha kuvvetli bağ mukavemeti oluşmasına sebebiyet vermiştir. Vakum uygulamasıyla üretilmiş kompozitler, vakumsuz üretilmiş kompozitlere göre daha düşük sürtünme katsayısı ve daha düzgün tribokimyasal tabakanın oluşmasına sebebiyet vererek daha iyi aşınma dayanımı sergilemişlerdir

Pure Al and alumina (2, 5, 10 wt.% Al2O3)-added Al composite foams were fabricated through powder metallurgy technique, where boric acid (H3BO3) is employed as a new alternative foaming agent. It is aimed to determine the effects of boric acid on the foaming behavior and cellular structure and also purposed to develop the mechanical properties of Al foams by addition of Al2O3. Al and Al composite foams with porosity fraction in the range of 46-53% were achieved by sintering at 620 °C for 2 h. Cell morphology was characterized using a combination of stereomicroscope equipped with image analyzer and scanning electron microscopy. Microhardness values were measured via using Vickers indentation technique. Quasi-static compression tests were performed at strain rate of 10−3 s−1. Compressive strength and energy absorption of the composite foams enhanced not only by the increasing weight fraction of alumina, but also by the usage of boric acid which leads to formation of boron oxide (B2O3) acting as a binder in obtaining dense cell walls. The results revealed that the boric acid has outstanding potential as foaming agent in the fabrication of Al and Al composite foams by providing improved mechanical properties.

SiAlON ceramics and their derivatives are potential materials for tribological applications where wear and friction are very crucial. TiN is a reinforcement phase and solid lubricant for SiAlON used to improve mechanical and tribological properties. In this study, alpha(1):beta(1)-SiAION composites incorporating nano- and micron-size TiN particles were produced by a gas pressure sintering method. Tribological behavior of the composites was investigated based on reinforcement particle size and physico-mechanical properties. Tribology tests were performed with a computer-controlled tribometer under dry unlubricated conditions with ball-on-disk configuration. It was found that the TiN particle size has an effect on surface roughness and hence the coefficient of friction. When the TiN particle size decreased to nano size, the wear mechanism was tribochemical, whereas, when the particle size increased to micron size, severe mechanical wear was observed besides tribochemical wear.

Al2O3 composites, comprising 10 wt% ZrO2 stabilized with 0.3 wt% MgO (MSZ/Al2O3) and 17.5–25 vol% cubic boron nitride (cBN)-added MSZ/Al2O3, were fabricated by spark plasma sintering technique, and the wear behavior of these composites was evaluated in terms of friction, wear rates, and wear mechanisms by ball-on-disk contact with dry and rotational sliding at room temperature against two different counterparts. The coefficient of friction (CoF) was smaller when sliding against tungsten carbide counterpart than in comparison with that sliding against sapphire ball for both with or without cBN-added composites. While the wear was characterized by a combination of mild abrasion and adhesion wear in the form of micro-cracking, micro-fragmentation, generation, and spalling of the oxidative tribochemical layer for the MSZ/Al2O3 composites, the experimental results have shown that the dominating wear was generated by a third-body wear for cBN-added composites via extraction of hard cBN grains from the matrix and related to density and hardness of the composites against both counterpart materials.

Although there are several researches focused on the improvement of strength of metal based foams by adding ceramic particles, the investigations of the effect of cubic boron nitride (cBN) reinforcement on the mechanism or properties of Al foams are very limited so far. In this study, it is aimed to develop and investigate the properties of Al matrix by cBN addition in different amounts (2, 5, 10 wt%). cBN/pure Al composite foams were fabricated by using boric acid (H3BO3) as foaming agent with the mean size of 500 μm under compacting pressure of 150 bar and sintering temperature 620 °C for 3 h at Ar atmosphere. The theoretical densities of sintered composite foams with porosity fraction of 50 vol% were measured according to Archimedes method. The phase analyses were conducted employing an XRD. The microstructures were studied by stereomicroscope equipped with image analyser. Compression tests were performed at the strain rate of 10−3 s−1 for evaluating the compressive behaviour and energy absorpt...

Yapilan calismada yaglayici ozelligi bulunan grafit dolgu elemaninin yuksek miktarlarda (hac.%25-52) epoksi matris icerisine ilave edilmesiyle epoksi matrisli kompozitin asinma direnci uzerine etkisi arastirilmistir. Epoksi matrisli kompozitler acik kaliplama teknigi ile uretilmistir. Grafit dolgulu kompozitlerin 3 noktali egme mukavemeti, egme modulu, sertlik, yogunluk olcumleri yapilmis ve mikroyapi gelisimleri incelenmistir. Asinma testleri 5N yuk altinda, 200m asinma mesafesine kadar ball-on-disk asinma cihazinda, oda sicakliginda gerceklestirilmistir. Fiziko-mekanik ozelliklerin ve mikroyapi gelisiminin asinma davranisi uzerine etkisi arastirilmistir. Sonuc olarak en iyi asinma direnci %30 grafit katkili kompozit malzemede elde edilmistir.

The powder mixtures of Ti, Si, TiC and Al were sintered to synthesize Ti3SiC2 and Ti3SiC2/SiC by spark plasma sintering (SPS) method. Single phase Ti3SiC2 and Ti3SiC2/SiC composites were obtained by sintering Ti/1.1Si/2TiC/0.2Al and 2.2Si/3TiC/0.2Al at 1400 °C, for 15 min, under a pressure of 50 MPa, respectively. The reduction of Al and Si contents in the starting powder mixture led to the formation of TiC impurity phase. X-ray diffraction (XRD) and Rietveld analyses were used to evaluate the phase constituents. The main objective of this study was to reveal the properties of single phase Ti3SiC2 and to evaluate the development of the mechanical and tribological properties of Ti3SiC2/SiC comprehensively. The results indicated that the SiC in situ reinforced Ti3SiC2 composites exhibited higher hardness, fracture toughness and wear resistance compared to single phase Ti3SiC2.

The demand for utilization of boron wastes related to the generation of massive amounts in each year is on the rise. In order to meet this growing need and demand for fabrication of environmentally friendly products, epoxy matrix composites containing 60wt% of boron wastes was developed. The influence of boron waste addition and the particle size of boron waste on epoxy matrix composites on physico-mechanical and tribological properties were evaluated. It was found that, hardness, flexural modulus and wear resistance properties were increased with the incorporation of boron wastes. Wear resistance increased with increasing boron waste particle size. The lowest specific wear rate was achieved for the largest particle size added composites. The physico-mechanical properties as well as microstructure wear behavior correlation were evaluated comprehensively.

The present study investigates the efficiency of spark plasma sintering (SPS) technique on the tribological behavior of tungsten carbide composites, and aims to develop the wear resistance of these composites by addition of cubic boron nitride (cBN). Wear tests of spark plasma sintered 6(wt.%)Co/WC, 25(vol%)cBN/6Co/WC and conventionally fabricated 6(wt.%)Co/WC as a reference sample were performed by ball-on-disk contact with dry and rotational sliding at room temperature in order to determine the friction coefficient and wear rate. Wear mechanisms were explained by using SEM observations and the wear rates were computed by a surface profilometer. In all cases, the major wear mechanisms were observed gradually in the form of microcraking, material removal by grain pull out, and generation and spalling of a tribochemical layer. Based on the experimental results, the addition of cBN considerably enhanced the wear resistance of tungsten carbides. In addition, these results revealed that SPS process has outstanding potential for the fabrication of tungsten carbides with high wear properties for tribological applications.

WOS: 000265152700025, 25 vol.% cubic boron nitride (cBN) added tungsten carbide (WC) powders containing 6 wt.% Co (WC-6Co) were densified by spark plasma sintering (SPS) technique under different experimental conditions and the effect of cBN addition on the microstructure, mechanical properties and thermal conductivity were investigated. Over 99.5% theoretical density was achieved for WC-6Co-cBN composites sintered at 1300 degrees C. under 75 MPa pressure for 7.5 min. Under these conditions, cBN -> hBN phase transformation was not observed

ÖZET Kompozit malzemeler, endüstrinin her alanında sağladıkları avantajlar nedeniyle, istenilen farklı tipteki mekanik, fiziksel veya kimyasal özellikleri yeterli olmayan polimer malzemelerin farklı tipte ve miktarlarda doğal lif ya da sentetik fiberler ile desteklenmesi sonucunda üretilen karma yapılı malzemelerdir. Özellikle lifli kompozit yapıların geliştirilmesi ve özellikleri üzerine, son zamanlarda çok sayıda çalışma bulunmaktadır. Bununla birlikte; yeni araştırmalar yapay fiberler yerine doğal fiberlerle üretilebilecek biyokompositlerin üretimi üzerine yoğunlaşmıştır. Bu çalışmalar kesik elyaf üretim süreçlerinde üretim yöntemlerinin geliştirilmesi ve aynı zamanda bu polimerlere ilişkin özellik profili geliştirilmesi ile ilgilidir. Yapılan çalışmanın biyokompozit oluşturabilecek atık sınıfında değerlendirilebilecek kadar ucuz doğal fiberlerin kompozit bileşiminde kullanılarak biyopolimerlerin üretilebilirliliğin araştırılması ve özelliklerinin tespitini kapsamaktadır.Bu çalışmada, doğal lif takviyeli kompozit malzemelerde takviye malzemesi olarak en çok kullanılan selüloz esaslı doğal lifler yerine yine lifli yapıya sahip çam kozalağı ve fındık kabuğu takviyesi kullanımı denenmiş, içyapıları, fiber-matris uyumu, özellikler üzerinde büyük etkisi olan fiber-matris bağ mukavemeti, kompozitlerin mekanik, fiziksel ve tribolojik özellikleri ayrıntılı olarak ilk defa incelenmiştir. Biyokompozitlerin üretilmesinde polietilen ve epoksi matris malzeme kullanılmıştır. Polietilen matrisli kompozitlerin üretiminde ekstrüzyon yöntemi, epoksi matrisli kompozitlerin üretiminde açık döküm yöntemi seçilmiştir. Proje kapsamında kompozit malzemelerin özelliklerine iki farklı takviye malzemesinin (öğütülmüş fındık kabuğu ve çam kozalağı) ve farklı miktarlarının (ağ. %5, %10, %20 ve %30) etkisi incelenmiştir. Farklı oran ve katkılara sahip kompozitlerin mekanik özelliklerin belirlenmesinde, sertlik, çekme ve eğme testleri gerçekleştirilmiştir. Tribolojik karakterizasyon için; tungsten karbür aşındırıcı bilye kullanılarak oda sıcaklığında yağlayıcı olmadan bilye-disk (ball-on-disk) testleri gerçekleştirilerek sürtünme ve aşınma oranları belirlenmiştir. Anahtar kelimeler: Biyokompozit malzemeler, biyopartikül, polimer, doğal atık SUMMARYComposite materials(CM) are made from two or more constituent materials with significantly different physical or chemical properties that, when combined, produce a material with characteristics different from the individual constituents. A number of research projects have been carried out in the past few years especially about developing production and processing technologies of fiber reinforced composite materials. Natural fiber-reinforced thermoplastic composites have attracted considerable attention in recent years because they can potentially cut product cost, improve mechanical properties, and are beneficial to the environment in applications. The investigations conducted ranged from the surface modifications, composite processing methods, to determination of physical properties. This study consists of investigation of properties and manufacturability of biocomposites by using low-cost biofibers classified as waste materials.In this study, the use of pine cones and hazelnut shell reinforcements which have been used as fiber reinforcing material in natural fiber reinforced composite materials instead of the most commonly used cellulose based natural fibers. Fiber-matrix bonding strength, fiber-matrix bond strength with great effect on properties, mechanical, physical and tribological properties of composites were investigated in detail for the first time. Polyethylene and epoxy matrix materials were used in the production of bio-composites. In the production of polyethylene matrix composites, extrusion method has been chosen for casting of epoxy matrix composites. Within the scope of the project, the effect of two different reinforcement materials (milled hazelnut shell and pine cone) and different amounts (10%, 20% and 30%) of the CM were investigated. For determination of the mechanical properties of composites with different ratios and additives, tensile, bending, hardness tests performed. For tribological characterization; by using tungsten carbide abrasive balls, ball-on-disk tests were carried out without lubricant at room temperature and friction and wear rates were determined.Keywords: Biocomposite Materials, Biofiber, Polymer, Waste Materials 67