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Investigation of the electrical conductivity and humidity sensitivity characteristics of BaTiO3 ceramics with PMMA additive

Ertug B., Boyraz T., Addemir O.

Archives of Metallurgy and Materials

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2012

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Vol. 57, iss. 2

437-442

EN

Humidity sensing is a requirement for human comfort and several industrial processes. There are two main types of humidity-sensing mechanisms. One of them is the protonic sensor which utilizes ionic conductivity due to water physisorption or capillary condensation in micropores. The semiconductor sensors use the changes in electronic conductivity due to water chemisorption. In this study, an ionic type of sensor was fabricated. Barium titanate based ceramic humidity sensors made with PMMA(Polymethyl metacrylate) as the PFA (Pore-forming agent) were investigated. All compositions included 0.18 wt. % of La2O3 and three different PMMA contents. The green compacts were heated at 1200-1500 º C for 2-6 h. in air and then furnace cooled. The fundamental characteristics of ceramic humidity sensors, electrical conductivity and humidity sensitivity were determined and discussed in relation to microstructural features, porosity, phase analysis and grain size data. The experimental results of conductivity measurements were evaluated in terms of practical sensor applications.

PL

Pomiar wilgotności jest istotny dla ludzkiej wygody i wielu procesów przemysłowych. Istnieją dwa główne typy mechanizmów wykrywania wilgoci. Jednym z nich jest czujnik protonic, który wykorzystuje przewodnictwo jonowe dzięki fizyko sorpcji wody lub kondensacji kapilarnej w mikroporach. Czujniki półprzewodnikowe wykorzystują zmiany przewodnictwa elektrycznego ze względu na chemisorpcje wody. W ramach niniejszej pracy, zbudowany został czujnik jonowy. Badane były ceramiczne czujniki wilgotności oparte o tytanian baru z dodatkiem PMMA (polimetakrylan metakrylanu) jako czynnika tworzenia porów. Wszystkie badane składy zawierały 0,18%.wag La2O3 i trzy różne zawartości PMMA. Zielone pakiety ogrzewano w temperaturze 1200-1500 º C przez 2-6 godzin w powietrzu, a następnie studzono razem z piecem. Podstawowe cechy ceramicznych czujników wilgotności, przewodność elektryczną i wrażliwość na wilgotność zostały określone i omówione w odniesieniu do cech mikrostruktury, porowatości, analizy fazowej i danych o wielkości ziarna. Eksperymentalne wyniki pomiarów przewodności były oceniane w kategoriach praktycznych zastosowań czujników.

2

Effects of B4C addition on the microstructural and thermal properties of hot pressed SiC ceramic matrix composites

Keçeli Z., Ögünç H., Boyraz T., Gökçe H., Addemir O., Lütfi Öveçođlu M.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 37, nr 2

428-433

EN

Purpose: The purpose of paper is to evaluate effects of B4C addition on the microstructural and thermal properties of hot pressed SiC ceramic matrix composites. Design/methodology/approach: The effect of B4C addition on microstructural and thermal properties of the SiC-B4C powder composites were investigated after high energy milling and hot pressing. SiC powders containing 5wt%, 10wt%, 15wt% B4C were mechanically alloyed in a high energy ball mill for 8 h. Findings: Microstructural characterisation investigations (SEM, XRD) were carried out on mechanically alloyed SiC powder composites containing 5 wt %, 10 wt %, 15 wt % B4C powders and on these powder composites sintered in vacuum at 50 MPa at 2100şC. The thermal properties were characterised using DTA, TGA and dilatometer. The results were evaluated. Research limitations/implications: In this study, the effect of B4C addition on microstructural and mechanical properties of the SiC-B4C powder composites was investigated after high energy milling and hot pressing. Originality/value: Ceramic matrix composite (CMC) material systems are stimulating a lot of interest to be used and provide unique properties for aircraft and land-based turbine engines, defence applications, rocket motors, aerospace hot structures and industrial applications. Boron carbide (B4C)-silicon carbide (SiC) ceramic composites are very promising armour materials because they are intrinsically very hard. Advanced SiC-based armour is desired so that the projectile is completely defeated without penetrating the ceramic armour.

3

Effects of B4C addition on the microstructural and thermal properties of hot pressed SiC ceramic matrix composites

Keceli Z., Ogunc H., Gokce H., Addemir O., Ovecoglu M. L., Boyraz T.

Archives of Materials Science

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2008

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Vol. 29, nr 1-2

41-49

EN

Ceramic matrix composite (CMC) material systems are receiving a great interest to be used and provides unique properties for aircraft and land-based turbine engines, defence applications, rocket motors, aerospace hot structures and industrial applications. Boron carbide (B4C)-silicon carbide (SiC) ceramic composites are very promising armor materials because they are intrinsically very hard. Advanced SiC-based armor is desired such that the projectile is completely defetaed without penetrating the ceramic armor. The effect of B4C addition on microstructural and thermal properties of the SiC-B4C powder composites were investigated after high energy milling and hot pressing. SiC powders containing 5wt%, 10wt%, 15wt% B4C were mechanically alloyed in a high energy ball mill for 8 h. Microstructural characterization investigations (SEM, XRD) were carried out on mechanically alloyed SiC powder composites containing 5 wt%, 10 wt%, 15 wt% B4C powders and on these powder composites sintered in vacuum at 50 MPa at 2100 degree C. The thermal properties were characterized using DTA, TGA and dilatometer. The results were evaluated.