SiC esaslı B4C takviyeli  seramiklerin mekanik, fiziksel ve balistik özelliklerinin incelenmesi
Investigation of physical, mechanical and ballistic properties of SiC based B4C reinforced ceramics
Yazar: TALHA ÇAVDAR
Danışman: PROF. DR. ŞADUMAN ŞEN
Sakarya Üniversitesi / Fen Bilimleri Enstitüsü / Metalurji ve Malzeme Mühendisliği Ana Bilim Dalı
Derece: Yüksek Lisans, 2024
Konu: Metalurji Mühendisliği = Metallurgical Engineering

Özet:
Bu çalışmada, silisyum karbür (SiC) esaslı bor karbür (B4C) katkılı kompozit seramiklerin üretimi ve kimyasal kompozisyon etkisinin seramiklerde meydana getirdiği fiziksel, mekanik ve balistik özellikleri incelenmiştir. 
SiC, yüksek sertlik, aşınma direnci ve termal stabilite gibi özelliklere sahip bir malzemedir. B4C ise sahip olduğu mükemmel sertlik ve düşük yoğunluk özelliğiyle bilinmektedir. Bu iki malzemeden elde edilen bileşim ile üstün mekanik ve fiziksel özelliklere sahip kompozit seramiklerin eldesi mümkün olmaktadır. 
Çalışma kapsamında kütlece %0-40 oranlarında B4C katkısı ile hazırlanacak olan SiC-B4C kompozit tozu farklı bağlayıcılar kullanılarak sulu yöntem ile hazırlanmıştır. Uygun nem ve tane boyut aralığına getirilen olan toz, 110 MPa/cm2 teorik basınç kullanılarak soğuk pres yöntemi ile şekillendirilmiştir. Şekillendirme işlemi yapılan malzemeler, bünyesindeki bağlayıcıların uçurulmasını ve sinterlenmesini içeren ısıl proseslere tabii tutulmuşlardır. 
Üretilen seramikler numuneler üzerinde, su emme, pişme küçülmesi, bulk yoğunluk, relatif yoğunluk, sertlik, üç nokta eğme mukavemeti, kırılma tokluğu gibi fiziksel ve mekanik özelliklerinin incelemeleri yapılarak bu incelemelere ait değerler tespit edilmiştir. Mikro yapı analizleri taramalı elektron mikroskobu (SEM) ve optik mikroskop (OM) ile yapılmış ve ayrıca sinterleme sonrası oluşan fazların karakterizasyonu X- Işınları Difraksiyonu (XRD) ile gerçekleştirilmiştir. 
Yapılan mekanik ve kimyasal testlerin yanı sıra üretilen seramiklerin balistik uygulamalardaki performansları da değerlendirilmiştir. Gerçekleştirilen balistik testler, yüksek hızda çarpan mühimmatlara karşı malzemenin dayanımını belirlemek amacıyla gerçekleştirilmiştir. Bu testler sonucunda, B4C takviyesi ile SiC esaslı seramiklerin balistik dayanımını önemli ölçüde artırdığı gözlenmiştir. 
Sonuçlar, B4C ilavesi ile SiC esaslı seramiklerin, sertlik, kırılma tokluğu ve balistik dayanım gibi özelliklerini iyileştirdiğini göstermiştir. Bu tip kompozit seramik malzemeler, özellikle zırh uygulamaları gibi yüksek performans gerektiren alanlarda büyük bir potansiyel barındırmaktadır.  
Bu çalışma yüksek sertlik, yüksek aşınma direnci ve balistik karakteristiklere sahip zırh seramiklerinin üretimini, mekanik, fiziksel ve balistik testlerinin gerçekleştirilmesini ve sonuçların tartışılmasını kapsar. Çalışma sonucunda SiC ve B4C kompozit malzemelerinin geliştirilmesi ve optimizasyonu için veriler sunulmakta ve endüstriyel uygulamalarda geliştirme amaçlanmaktadır.

Abstract:
This study investigates the production and the effects of chemical composition on the physical, mechanical, and ballistic properties of silicon carbide (SiC) based composite ceramics reinforced with boron carbide (B4C). SiC is known for its high hardness, wear resistance, and thermal stability, making it a valuable material in various industrial applications. B4C, on the other hand, is renowned for its exceptional hardness and low density. Combining these two materials can yield composite ceramics with superior mechanical and physical properties, which are highly desirable in applications requiring robust performance and durability.
The primary objective of this study is to develop SiC-based composite ceramics with varying proportions of B4C and to examine the influence of these compositions on the resulting material properties. Specifically, the research focuses on understanding how B4C addition affects the physical, mechanical, and ballistic characteristics of the SiC matrix. The goal is to determine the optimal B4C content that maximizes the desired properties while maintaining the structural integrity of the composite.
In this study, composite powders were prepared with B4C additions of 0%, 10%, 20%, 30%, and 40% by weight. Different binders were used to prepare these powders via an aqueous method. The powders were then conditioned to achieve appropriate moisture and particle size ranges. The conditioned powders were shaped using a cold press method at a theoretical pressure of 110 MPa/cm². These shaped materials underwent thermal processes that included binder removal and sintering to achieve the final ceramic structure.
The preparation of the SiC-B4C composite powders involved meticulous processes to ensure homogeneity and uniform particle distribution. The powders were mixed with binders in an aqueous solution to form a slurry, which was then dried to obtain granules with the desired particle size. These granules were sieved to ensure uniformity before being subjected to the cold press method.
The shaping process involved compressing the granules into green bodies using a cold press under high pressure. The green bodies were then subjected to thermal treatments to remove the binders and to sintering the composite materials. The sintering process was carefully controlled to avoid excessive grain growth and to ensure the formation of a dense and uniform microstructure.
The produced ceramic samples were subjected to various tests to determine their physical and mechanical properties. The evaluations included water absorption, firing shrinkage, bulk density, relative density, hardness, three-point bending strength, and fracture toughness. Microstructural analyses were conducted using scanning electron microscopy (SEM) and optical microscopy (OM), and the phases formed after sintering were characterized using X-ray diffraction (XRD).
The physical properties of the composites, such as water absorption and bulk density, were measured to evaluate the effectiveness of the sintering process and the integrity of the composite structure. Low water absorption and high bulk density are indicative of a well-sintered, dense material with minimal porosity.
The mechanical properties, including hardness, three-point bending strength, and fracture toughness, were assessed to determine the load-bearing capacity and the resistance to crack propagation of the composites. These properties are critical for applications where mechanical durability and resistance to mechanical stresses are required.
In addition to mechanical and chemical testing, the ballistic performance of the produced ceramics was evaluated. Ballistic tests were performed to assess the material's resistance to high-velocity impacts. These tests involved subjecting the ceramics to impacts from projectiles at various speeds and angles to simulate real-world ballistic threats. The performance was measured in terms of the material's ability to absorb and dissipate the energy of the impacts without catastrophic failure.
The results demonstrated that the addition of B4C significantly enhances the properties of SiC-based ceramics. The findings indicated improvements in hardness, fracture toughness, and ballistic resistance. The microstructural analyses showed a uniform distribution of B4C within the SiC matrix, contributing to the observed property enhancements.
The SEM and OM analyses revealed that the addition of B4C to the SiC matrix led to the formation of a well-distributed secondary phase within the composite. This distribution was crucial in improving the mechanical properties, as the B4C particles acted as reinforcement agents that impeded crack propagation and enhanced the overall toughness of the material.
The XRD analysis confirmed the presence of distinct phases in the sintered composites. The formation of these phases was consistent with the expected chemical reactions during sintering and indicated successful incorporation of B4C into the SiC matrix. The phase composition was correlated with the observed improvements in mechanical and ballistic properties.
The increase in B4C content led to a noticeable improvement in the mechanical properties. Specifically, the hardness and fracture toughness of the composites increased with higher B4C additions. The enhanced hardness was attributed to the intrinsic hardness of B4C, while the improved fracture toughness was due to the effective load transfer between the SiC matrix and the B4C reinforcements.
The ballistic tests further confirmed that the B4C-reinforced SiC ceramics exhibited superior performance against high-velocity impacts, making them suitable for armor applications. The ceramics demonstrated the ability to absorb and dissipate the energy from the impacts, thereby preventing penetration and minimizing damage. The performance was evaluated based on the residual strength of the materials and their ability to maintain structural integrity after impact.
This study concludes that the addition of B4C to SiC-based ceramics significantly improves their mechanical and ballistic properties. These composite ceramics exhibit high hardness, enhanced fracture toughness, and excellent ballistic resistance, making them ideal candidates for high-performance applications, particularly in armor systems. The data obtained from this research provide valuable insights for the development and optimization of SiC-B4C composite materials for industrial applications.
Future research could focus on further optimizing the production processes and exploring additional applications for these advanced composite materials. Potential areas of investigation include the use of alternative sintering techniques, the incorporation of additional reinforcement phases, and the development of new composite formulations with tailored properties for specific applications. The insights gained from this study lay the groundwork for continued advancements in the field of composite ceramics and their industrial applications.