SiC와 $ZrO_2$를 함유하는 ${Al_2}{O_3}$ 입자복합체의 균열저항거동 : I. 실험

박관수,이승환,이재형 한국세라믹학회 2000 한국세라믹학회지 Vol.37 No.4

Particulate composites of Al2O3/SiC, Al2O3/ZrO2 and Al2O3/ZrO2/SiC have been fabricated to investigate their R-curve behaviors and toughening mechanisms. Al2O3 containing 30 vol% SiC particles of 3${\mu}{\textrm}{m}$ showed rising R-curve behavior owing to the strong crack bridging by SiC particles. The fracture toughness reached 9.1 MPa {{{{ SQRT {m} }} at the crack length of 1000${\mu}{\textrm}{m}$. On the other hand, ZrO2-toughened Al2O3 had a high flat R-curve since it rose steeply in the short crack region due to the well known transformation toughening. For Al2O3/ZrO2/SiC composites, the R-curve behavior was similar to that of Al2O3/SiC but with slightly higher toughness. The SiC particles in this composite decreased the amount of transformable tetragonal phase to reduce the effect of transformation toughening by 50%. It was also found that the fracture toughness of this composite with two different toughening mechanisms was markedly lower than that estimated by the simple addition of two contributions.

Processing and properties of Ni dispersed zirconia toughened alumina

Mayssam Hussein Nabbouh,Rahim Naghizadeh,Farhad Golestani-Fard,Hamid Reza Rezaie 한양대학교 세라믹연구소 2017 Journal of Ceramic Processing Research Vol.18 No.9

The combination of phase transformation of zirconia and plastic deformation of Ni metal has shown a significant improvement in toughness caused by the synergistic toughening. In the present study, the reduction process within a carbon bed, the effectof Ni content on densification, microstructure and mechanical properties of ZTA/Ni composites was investigated. Powder mixtures of Al2O3, 3YSZ, and nickel nitrate as a source of Ni metal were prepared by precipitated Ni on ceramic powders to obtained ZTA/Ni composites. The composites were pressureless sintered at 1600 o C for 3 hrs within a carbon powder bed. The results showed that the addition of 5 vol.% Ni results in the highest relative density of 93% and the maximum fracture strength and toughness values of 348 MPa and 3.32 MPa.m½, respectively.

Influences of nano-3Y-TZP reinforcement on phase transformation and crystallite size modification of zirconia-toughened alumina and Rietveld refinement of crystallographic data

Dhar Sajib Aninda,Sarker Saugata,Mumu Homayra Tabassum,Rashid A. K. M. Bazlur 한국세라믹학회 2023 한국세라믹학회지 Vol.60 No.2

The effects of varying amount of nano-3 mol% yttria-stabilized zirconia addition on the crystal structures, mechanical, and microstructural properties of zirconia-toughened alumina (ZTA) composite have been investigated in this work. The ZTA specimens were prepared by different 3Y-TZP amount ranging from 9 to 18 wt.% and sintered at 1550 °C for 2 h. The densification behaviour, indentation fracture toughness, microhardness, elastic modulus, flexural strength and surface morphology of the composites have been determined and correlated with tetragonal → monoclinic phase transformation and retention of tetragonal phase. Rietveld refinement of the crystallographic data was performed to correlate the effect of zirconia addition on the phase compositions, t → m transformability and impacts on crystallite sizes and lattice parameter. The toughness and flexural strength of the composites improved significantly up to 15 wt.% YSZ addition followed by a reduction for 18 wt.%, while the hardness and elastic modulus decreased with YSZ addition. Rietveld refinement ascertains the metastable t-ZrO2 retention and thermodynamically stable m-ZrO2 transformation with increasing 3Y-TZP and subsequent enhancement in fracture toughness through transformation toughening.

AE(Acoustic Emission)에 의한 세라믹 복합재료의 고인성화 기구 분석

장병국 한국세라믹학회 1997 한국세라믹학회지 Vol.34 No.11

Al2O3/20 vol%YAG composite containing equiaxed grains and Al2O3/20 vol%LaAl11O18 composite containing elongated grains were fabricated using Al2O3-Y2O3 composition and Al2O3-La2O3 composition, respectively, by hot-pressing. In order to investigate the influence of microstructural control of second phase on toughening effect of toughened ceramic composites, AE (acoustic emission) measurements have been coupled with fracture toughness experiments(SENB and SEPB method). A separation of the fracture toughness and analysis of toughening mechanism was possible using the AE technique. The fracture toughness of hot-pressed materials was estimated to be 3.2 MPam0.5 for monolithic alumina, 4.7 MPam0.5 for Al2O3/20 vol%YAG composite and 6.2 MPam0.5 for Al2O3/20 vol%LaAl11O18 composite. In monolithic Al2O3, toughening does not occur as a result of either microcracking or grain bridging, whereas, composites exhibit toughening effects by both microcracking in the frontal zone and gain bridging in the wake zone, resulting in an improvement of fracture toughness as compared with monolithic Al2O3. The fracture toughness of Al2O3/20 vol%LaAl11O18 composite is higher than that of Al2O3/20 vol%YAG composite. It may be attributed to the elongated microstructure of Al2O3/20 vol%LaAl11O18 composite, resulting relatively greater bridging effect.

에폭시 강인성 향상 첨가제의 적용 및 물성 분석

김대연 ( Daeyeon Kim ),김순천 ( Soonchoen Kim ),박영일 ( Young Il Park ),김영철 ( Young Chul Kim ),임충선 ( Choong Sun Lim ) 한국접착및계면학회 2015 접착 및 계면 Vol.16 No.3

코어/쉘 나노입자, CTBN 변성에폭시, 폴리에스터 폴리올, 폴리우레탄 등과 같은 다양한 종류의 강인화 소재는 에폭시 수지의 주요 단점으로 알려진 취성을 보완하여 낮은 충격 저항성을 개선시키기 위한 방법으로 연구되고 있다. 본 연구에서는 앞서 언급된 강인화 소재를 선정, 접착제 조성물에 첨가하여 기계적 물성을 조사하였다. 강인화 소재 도입에 따른 기계적 강도의 측정은 UTM을 이용한 굴곡 강도와 탄성률 측정 및 Izod 충격 시험기를 사용한 충격 강도 실험을 통해 이루어 졌으며, 그 결과 강인화 소재가 에폭시 경화물의 유연성 및 충격에 대한 저항성 향상에 미치는 긍정적인 효과가 나타남을 관찰하였다. 또한, DMA를 이용한 저장 탄성률 결과는 굴곡 탄성률의 결과와 동일한 경향으로 나타남을 확인하였다. 강인화 소재가 충격 강도 향상에 영향을 주는 이유는 에폭시 수지에 첨가된 강인화 소재의 상 분리 현상에 의한 것이며, 상 분리된 강인화 소재는 에폭시 조성물의 파단면을 관찰한 FE-SEM 이미지에서 관찰하였다. Epoxy resin toughening agents such as core/shell nanoparticles, CTBN epoxy, polyester polyols, and polyurethane have been widely used in order to compensate for the brittleness and improve the impact resistance of the epoxy resin. In this work, a few tougheners mentioned above were individually added into adhesive compositions to observe the effects of physical and mechanical properties. Both flexural strength and flexural modulus were measured with UTM while impact strength was analyzed with Izod impact tester. The obtained results showed that the addition of toughening agents afforded positive performance in terms of flexibility and impact resistance of the cured epoxy resin. Furthermore, DMA experiments suggested that the trends of storage modulus data of each epoxy resin composition coincided with the trends of flexural modulus data. FE-SEM images showed that toughening agents formed circled-shape particles when it was cured in epoxy resin composition at high temperature by phase separation. The existence of particles in the cured samples explains why epoxy resin with toughener has higher impact resistance.

Brittle–Ductile Transitions of Rubber Toughened Polypropylene Blends: A Review

Jung-Wook Wee,Alexander Chudnovsky,Byoung-Ho Choi 한국정밀공학회 2024 International Journal of Precision Engineering and Vol.11 No.4

Polypropylene (PP) blended with rubber particles has been recognized for significantly increasing impact resistance, which is increasingly demanded in industries such as electric vehicles and consumer electronics. However, a comprehensive understanding of the toughening mechanisms underlying these lightweight impact-resistant materials is imperative for future research. This article provides a detailed review of the ductile-to-brittle (DB) transition behavior and the improvements in impact resistance observed in rubber-toughened PP blends. Firstly, the fracture behavior of homogeneous PP is summarized across different strain rates and temperatures, including the DB transition and yielding and crazing criteria. Furthermore, the influence of notches and defects on the DB transition is discussed extensively. Subsequently, the article examines the theoretical and practical aspects of the toughening mechanisms facilitated by the rubber phase in PP-rubber blends. The percolation model is used to investigate the inter-distance criterion between neighboring rubber particles and the impact of particle size and content on toughening behavior. The primary objective of this article is to enhance the understanding of the toughening behavior exhibited by PP and rubber blends. Additionally, this study aims to provide valuable insights for developing advanced lightweight materials using PP-based blends for various industrial applications.

The effects of toughening materials in epoxy-based adhesive

김대연,김순천,박영일,김영철,임충선 한국공업화학회 2014 한국공업화학회 연구논문 초록집 Vol.2014 No.1

Epoxy resins that have excellent thermal and mechanical properties are widely used in many adhesive applications that range from common type to high performance type as a main matrix material. However, It is difficult to use binder system composed with neat epoxy resin and amine-type curing agent for high performance adhesive because of its high brittleness and poor resistance to crack propagation. Epoxy-based adhesive with toughening material shows improved flexibility and high performance of adhesion properties. In this research, a couple of toughening materials such as polyurethane, polyester polyol, Core/Shell nanoparticles, and liquid rubber-modified resin were incorporated in cured epoxy/dicyandiamide system to improve impact resistance. The morphology of each toughening material on the fracture surface of the cured sample was analyzed with FE-SEM. The adhesion strength in shear and T-peel by tension loading will be discussed.

Rubber Toughened Epoxy

Ratna, D.,Banthia, Ajit K. The Polymer Society of Korea 2004 Macromolecular Research Vol.12 No.1

Toughening of epoxy resins for improvement of crack resistance has been the subject of intense research interest during the last two decades. Epoxy resins are successfully toughened by blending with a suitable liquid rubber, which initially remains miscible with epoxy and undergoes a phase separation in the course of curing that leads to the formation of a two-phase microstructure, or by directly blending preformed rubbery particle. Unlike the situation for thermoplastics, physical blending is not successful for toughening epoxy resins. Recent advances in the development of various functionalized liquid rubber-based toughening agents and core-shell particles are discussed critically in this review.

Al$_2$O$_3$/LaAl$_{11}$O$_{18}$ 복합재료의 인성증진

장병국,우상국 한국세라믹학회 1998 한국세라믹학회지 Vol.35 No.12

Al2O3/(5~20vol%)LaAl11O18 composites in which the second phase was dispersed with a elongated grain shape were fabricated using Al2O3 and La2O3 composition by hot-pressing. In order investigate the in-fluence of LaAl11O18 on the toughening of LaAl11O18 on the toughening of Al2O3 matrix composites AE(acoustic emission) analysis was con-ducted together with an evaluation of fracture toughness using of SEPB technique. The degree of AE events occurred in composites were more than those in monolithic alumina. The occurrences of AE event increased with increasing the amount of LaAl11O18 phase in the Al2O3/LaAl11O18 composite is two times higher compared to monolithic alu-mina. The main toughening mechanism was attributed to the bridging of LaAl11O18 grains at tip of pro-pagating crack.

Toughening of melamine–formaldehyde foams and advanced applications based on functional design

Bing Song,Xueli Zhu,Wei Wang,Liang Wang,Xiaoyuan Pei,Xiaoming Qian,Liangsen Liu,Zhiwei Xu 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.119 No.-

Owing to the intrinsic flame-retardancy, thermal stability, sound absorption, and easy processing, melamine–formaldehyde foams(MFs) have drawn substantial attention. Typically, the high-porosity and compressibilityof flexible MFs render them suitable for the construction of 3D templates and in thefabrication of porous N-doped carbon materials. But the widespread applications of MFs still suffer highbrittleness and low strength, calling for modifying and toughening MFs with more facile and economicalmethods, and much potential in advanced applications by functional design deserves further exploration. This review comprehensively summarized and evaluated the recent progress of the toughening methodsof MFs. We will also look into the applications of commercial MFs, carbonized MFs and foam-based compositesin flame retardancy and thermal management, oil/water separation, photothermal conversion,electrical energy storage, and other fields, aiming to give a guide for the preparation, modification, andexploitation of MFs both in traditional and emerging areas.