Ciência & Tecnologia dos Materiais最新文献_第9页

Influence of processing conditions on crystal structure of BiNbO4 ceramics 工艺条件对BiNbO4陶瓷晶体结构的影响

Ciência & Tecnologia dos Materiais Pub Date : 2017-01-01 DOI: 10.1016/j.ctmat.2016.03.003

Agata Lisińska-Czekaj , Dionizy Czekaj , Julian Plewa

{"title":"Influence of processing conditions on crystal structure of BiNbO4 ceramics","authors":"Agata Lisińska-Czekaj , Dionizy Czekaj , Julian Plewa","doi":"10.1016/j.ctmat.2016.03.003","DOIUrl":"10.1016/j.ctmat.2016.03.003","url":null,"abstract":"<div>Bismuth niobate (BiNbO4) has attracted attention as a low-fired ceramics with promising microwave application potential. It belongs to the bismutocolumbite oxides with similarly to scheelite-like stibiotantalite structure (SbTaO4) A3+B5+O4. The aim of the present research was to fabricate BiNbO4 ceramics by solid state reaction route from the mixture of simple oxides viz. Bi2O3, and Nb2O5, and study its phase composition as well as crystal structure by X-ray diffraction method. The Rietveld refinement method was utilized for analysis of diffraction patterns. It was found that the mass change effects finished at temperature T=500°C and the total mass change was about Δm=-0.78%. It was found that BiNbO4 ceramics sintered in ambient air exhibited multiphase composition, i.e., apart from the major α-BiNbO4 phase, the orthorhombic Bi5Nb3O15, Bi3Nb17O47 and cubic Bi3NbO7 phases were present. An increase in sintering temperature caused an increase in the amount of major α-BiNbO4 phase which adopted an orthorhombic symmetry described well by Pnna(52) space group.</div>","PeriodicalId":10198,"journal":{"name":"Ciência & Tecnologia dos Materiais","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.ctmat.2016.03.003","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83676527","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Experimental characterization of ceramic shells for investment casting of reactive alloys 反应性合金熔模铸造用陶瓷壳的实验表征

Ciência & Tecnologia dos Materiais Pub Date : 2017-01-01 DOI: 10.1016/j.ctmat.2016.07.014

Rui Neto, Teresa Duarte, Jorge Lino Alves, Francisco Torres

{"title":"Experimental characterization of ceramic shells for investment casting of reactive alloys","authors":"Rui Neto, Teresa Duarte, Jorge Lino Alves, Francisco Torres","doi":"10.1016/j.ctmat.2016.07.014","DOIUrl":"10.1016/j.ctmat.2016.07.014","url":null,"abstract":"<div>The investment casting of reactive Ti and TiAl alloys requires the use of selected ceramics in the face-coat layer to prevent the reaction between the cast metal and ceramic shell, avoiding the formation of a hard layer at the metallic components surface. This work aims to study the influence of ceramic shells composition in some of its characteristics such as flexural strength, friability and dimensional accuracy. The microstructure of the shells was evaluated by SEM. Changes in the face-coat and back-up ceramic shells composition determines the ceramic shell strength to withstand the casting stage with adequate mould permeability and thermal conductivity, and a compromise resistance for knock-out. All the non-conventional ceramic shell systems with interest for reactive alloys, based on fumed alumina binder and alumina sand for the back-ups, present higher dimensional stability (low shrinkage or expansion) compared with traditional systems based on colloidal silica binder and zircon and aluminosilicates back- ups. In this work, better mechanical strength and lower friability were obtained with non-conventional face-coats of alumina and polymer binders, both with yttria flour and stucco, followed by alumina back-ups. Selecting the right ceramic shell composition, it is possible to achieve adequate properties for casting titanium alloys.</div>","PeriodicalId":10198,"journal":{"name":"Ciência & Tecnologia dos Materiais","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.ctmat.2016.07.014","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87972988","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2

Urbcork – Urban furniture with application of high density cork 城市软木-应用高密度软木的城市家具

Ciência & Tecnologia dos Materiais Pub Date : 2017-01-01 DOI: 10.1016/j.ctmat.2016.06.005

Mariana Alves , Lígia Lopes , Jorge Lino Alves , Francisco Xavier de Carvalho

{"title":"Urbcork – Urban furniture with application of high density cork","authors":"Mariana Alves , Lígia Lopes , Jorge Lino Alves , Francisco Xavier de Carvalho","doi":"10.1016/j.ctmat.2016.06.005","DOIUrl":"10.1016/j.ctmat.2016.06.005","url":null,"abstract":"<div>Urbcork is an urban furniture line developed at the Faculty of Engineering of the University of Porto (FEUP) for the collection produced by Leets Urban Design. It can be highlighted for its sustainable properties and inclusive design concerns.Urban furniture is a product to be used by a large number of people in a public space. It has a high level of wear and ageing due to the intensive use, solar exposure and weather conditions.During the project development there was a conceptual idea about using cork as the main material for the seat and the back. The opportunity of developing a prototype brought the question about how to keep cork properties after a long exposure on exterior.The main line of investigation was about how to protect cork keeping its natural appearance and extending its properties and conservation over time. Laboratory tests held at CTCOR and FEUP were conducted in order to understand the behaviour of cork on extreme conditions. The results are not yet successful, but with more tests, the product can be well accepted in the international market.</div>","PeriodicalId":10198,"journal":{"name":"Ciência & Tecnologia dos Materiais","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.ctmat.2016.06.005","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87942998","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Shear fracture toughness and cohesive laws of adhesively-bonded joints 粘接接头剪切断裂韧性及粘接规律

Ciência & Tecnologia dos Materiais Pub Date : 2017-01-01 DOI: 10.1016/j.ctmat.2016.05.003

J.C.S. Azevedo, R.D.S.G. Campilho, F.J.G. Silva

{"title":"Shear fracture toughness and cohesive laws of adhesively-bonded joints","authors":"J.C.S. Azevedo, R.D.S.G. Campilho, F.J.G. Silva","doi":"10.1016/j.ctmat.2016.05.003","DOIUrl":"10.1016/j.ctmat.2016.05.003","url":null,"abstract":"<div>Adhesive bonding is a viable technique to reduce weight and complexity in structures. Additionally, this joining technique is also a common repair method for metal and composite structures. However, a generalized lack of confidence in the fatigue and long-term behaviour of bonded joints hinder their wider application. Suitable strength prediction techniques must be available for the application of adhesive bonding, and these can be based on mechanics of materials, conventional fracture mechanics or damage mechanics. These two last methodologies require the knowledge of the fracture toughness (GC) of materials. Being damage mechanics-based, Cohesive Zone Modelling (CZM) analyses coupled with Finite Elements (FE) are under investigation. In this work, CZM laws were estimated in shear for a brittle adhesive (Araldite® AV138) and high-strength aluminium adherends, considering the End-Notched Flexure (ENF) test geometry. The CZM laws were obtained by an inverse methodology based on curve fitting, which made possible the precise estimation of the adhesive joints’ behaviour. It was concluded that a unique set of shear fracture toughness (GIIC) and shear cohesive strength (ts0) exists for each specimen that accurately reproduces the adhesive layer behaviour. With this information, the accurate strength prediction of adhesive joints in shear is made possible by CZM.</div>","PeriodicalId":10198,"journal":{"name":"Ciência & Tecnologia dos Materiais","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.ctmat.2016.05.003","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85869199","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Instrumentation and characterization of materials for hydrogen storage 储氢材料的仪器和表征

Ciência & Tecnologia dos Materiais Pub Date : 2016-07-01 DOI: 10.1016/j.ctmat.2017.01.002

Edivagner S. Ribeiro, João M. Gil

引用次数: 2

Strategies on implementing a potential self-healing functionality in a composite structure 在复合结构中实现潜在自修复功能的策略

Ciência & Tecnologia dos Materiais Pub Date : 2016-07-01 DOI: 10.1016/j.ctmat.2016.05.001

X. Tsilimigkra , A. Baltopoulos , S. Tsantzalis , A. Kotrotsos , N. Siakavellas , V. Kostopoulos , S. Flórez

{"title":"Strategies on implementing a potential self-healing functionality in a composite structure","authors":"X. Tsilimigkra , A. Baltopoulos , S. Tsantzalis , A. Kotrotsos , N. Siakavellas , V. Kostopoulos , S. Flórez","doi":"10.1016/j.ctmat.2016.05.001","DOIUrl":"10.1016/j.ctmat.2016.05.001","url":null,"abstract":"<div>Deteriorations generated in service can cause catastrophic failure at the specific properties of the polymer composite materials. In view of this, scientists have drawn inspirations by natural biological systems and their unique ability to heal an external wound, to develop a similar repair system within a material. Carbon and glass fiber reinforced polymers were manufactured following the wet lay up or the prepreg process. Microcapsules at contents, 5% or 10% by weight, vascular networks from wax and steel wires and finally reversible polymers were implemented within a composite as a potential self-healing system. Inspection techniques, including Ultrasonic C-Scan and Infrared Thermography, were applied, where possible. Optical microscopy revealed the disruption of the composite structural integrity, regarding the observed ply waviness and the resin reach zones around the vascular structures. Three point bending experiments determined the knock down factor, expressed as a decrease on flexural strength and modulus values, for each case, compared to the reference material. The reduction ranged from 12%-64% depending mainly not only to the selected manufacturing method but also to the different implemented healing system.</div>","PeriodicalId":10198,"journal":{"name":"Ciência & Tecnologia dos Materiais","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.ctmat.2016.05.001","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74434373","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 8

Key issues to high electroactivity for methanol oxidation and oxygen reduction of Pt-based supported catalyst in fuel cells relevant environment pt基负载型催化剂在燃料电池中高电活性甲醇氧化和氧还原的关键问题

Ciência & Tecnologia dos Materiais Pub Date : 2016-07-01 DOI: 10.1016/j.ctmat.2017.01.001

A.I. de Sá , A. Capelo , A. Esteves , L. Cangueiro , A. Almeida , R. Vilar , C.M. Rangel

引用次数: 1

Research on materials and renewable energy 材料与可再生能源研究

Ciência & Tecnologia dos Materiais Pub Date : 2016-07-01 DOI: 10.1016/j.ctmat.2017.02.003

Luís Gil

引用次数: 1

Electrical and electrochemical properties of titanium dioxide /graphene nano platelets cathode for magnesium battery applications 用于镁电池的二氧化钛/石墨烯纳米片阴极的电学和电化学性能

Ciência & Tecnologia dos Materiais Pub Date : 2016-07-01 DOI: 10.1016/j.ctmat.2017.02.002

M.H. Makled , Y.M. Arabi , E. Sheha , S. Arfa , I.S. Yahia , F. Salman

引用次数: 1

Water management in PEMFC: 1-D model simulations PEMFC中的水管理:一维模型模拟

Ciência & Tecnologia dos Materiais Pub Date : 2016-07-01 DOI: 10.1016/j.ctmat.2016.12.001

D.S. Falcão, C. Pinho, A.M.F.R. Pinto

引用次数: 6