scholarly journals Shrinkage mechanism and phase evolution of fine-grain BaTiO3 powder compacts containing 10mol% BaGeO3 prepared via a precursor route

2008 ◽  
Vol 112 (2) ◽  
pp. 531-535 ◽  
Author(s):  
Roberto Köferstein ◽  
Lothar Jäger ◽  
Mandy Zenkner ◽  
Thomas Müller ◽  
Hans-Peter Abicht
Keyword(s):  
Phase Evolution ◽  
Batio3 Powder ◽  
Fine Grain ◽  
Precursor Route ◽  
Powder Compacts

scholarly journals Shrinkage mechanism and phase evolution of fine-grain BaTiO3 powder compacts containing 10 mol% BaGeO3 prepared via a precursor route

2018 ◽  
Author(s):  
Roberto Köferstein
Keyword(s):  
Mixed Oxide ◽  
Sintering Temperature ◽  
Phase Evolution ◽  
Batio3 Powder ◽  
Fine Grain ◽  
Initial Stage ◽  
Dense Ceramic ◽  
Precursor Route ◽  
Powder Compacts ◽  
Barium Titanium

The shrinkage mechanism of BaTiO3 powder compacts containing 10 mol%BaGeO3, synthesized by a precursor route and a conventional mixed-oxide method, aredescribed herein. The calcination of a barium titanium germanium 1,2-ethanediolato complexprecursor - [Ba(HOC2H4OH)4][Ti0.9Ge0.1(OC2H4O)3] (1) - at 730 °C leads to a nm-sizedBa(Ti0.9/Ge0.1)O3 powder (1a) (SBET = 16.9 m2/g) consisting of BaTiO3 and BaGeO3. Whereasthe conventional mixed-oxide method yields a powder (2) with a specific surface area of SBET= 2.0 m2/g. Powder compacts of 1a start to shrink at 790 °C and the shrinkage rate reaches amaximum at 908 °C. Dense ceramic bodies can be obtained below the appearance of theliquid melt (1120 °C), therefore the shrinkage of 1a can be described by a solid-state sinteringmechanism. Otherwise the beginning of the shrinkage of powder 2 is shifted to highertemperatures and the formation of the liquid melt is necessary to obtain dense ceramic bodies. Isothermal dilatometric investigations indicate that the initial stage of sintering is dominatedby sliding processes. XRD investigations show that below a sintering temperature of 1200 °Cceramic bodies of 1a consist of tetragonal BaTiO3 and hexagonal BaGeO3, whereastemperatures above 1200 °C lead to ceramics containing orthorhombic BaGeO3, and atemperature of 1350 °C causes the formation of a Ba2TiGe2O8 phase. The phase evolution ofceramic bodies of 2 is similar to 1a, however a Ba2GeO4 phase is observed below atemperature of 1100 °C.

scholarly journals Preparation and Sintering Behaviour of a Fine Grain BaTiO3 Powder containing 10 mol% BaGeO3

2018 ◽  
Author(s):  
Roberto Köferstein
Keyword(s):  
Dielectric Constant ◽  
Specific Surface ◽  
Solid Solutions ◽  
Relative Permittivity ◽  
Phase Evolution ◽  
Batio3 Powder ◽  
Fine Grain ◽  
Rate Controlled ◽  
Sintering Behaviour ◽  
Powder Compacts

The formation of solid solutions of the type [Ba(HOC2H4OH)4][Ti1-xGex(OC2H4O)3] as Ba(Ti1-x/Gex)O3 precursors and the phase evolution during thermaldecomposition of [Ba(HOC2H4OH)4][Ti0.9Ge0.1(OC2H4O)3] (1) are described herein. The 1,2-ethanediolato complex 1 decomposes above 589 °C to a mixture of BaTiO3 and BaGeO3. Aheating rate controlled calcination procedure up to 730 °C leads to a nm-sizedBa(Ti0.9/Ge0.1)O3 powder (1a) with a specific surface area of S = 16.9 m2/g, whereas aconstant heating rate calcination at 1000 °C for 2 h yields a powder (1b) of S = 3.0 m2/g. Theshrinkage and sintering behaviour of the resulting Ba(Ti0.9/Ge0.1)O3 powder compacts incomparison with nm-sized BaTiO3 powder compacts (2a) has been investigated. A 2-stepsintering procedure of nm-sized Ba(Ti0.9/Ge0.1)O3 compacts (1a) leads below 900 °C toceramic bodies with a relative density of ³ 90 %. Furthermore, the cubic ? tetragonal phasetransition temperature has been detected by dilatometry and the temperature dependence ofthe dielectric constant (relative permittivity) has also been measured.

Microstructure and tribology of laser mixed Fe/Ti/C multilayered films on AISI 304 stainless steel

1990 ◽  
Vol 5 (6) ◽  
pp. 1207-1214 ◽  
Author(s):  
M. Nastasi ◽  
J-P. Hirvonen ◽  
T. G. Zocco ◽  
T. R. Jervis
Keyword(s):  
Stainless Steel ◽  
Tribological Properties ◽  
Laser Fluence ◽  
Chemical Reactivity ◽  
Phase Evolution ◽  
304 Stainless Steel ◽  
Multilayered Films ◽  
Carbide Phases ◽  
Fine Grain ◽  
Wear And Friction

An excimer laser was used to mix Fe/Ti/C multilayered films on 304 stainless steel substrates. The samples were processed at both 1.1 and 1.7 J/cm2 with the number of pulses at each position varied between 1 and 10. Composition, microstructure, phase evolution, and tribological properties were observed to correlate with total laser fluence. Increases in Fe concentration from substrate interdiffusion and loss of C content were observed with increasing total laser fluence. The best tribological properties were observed in films possessing a combination of an amorphous or Fe3C phase plus fine grain TiC following processing at low and intermediate total laser fluence. At higher total fluences a combination of α-Fe, Fe3C, and fine-grain TiC was observed along with degradation in the wear and friction properties. Under optimum laser processing conditions the modified surface had a friction coefficient under dry sliding conditions reduced by a factor of 2 relative to uncoated 304 stainless steel and was significantly more wear resistant. These improvements in wear and friction appear to be related to the reduced chemical reactivity of the amorphous and carbide phases and to the influence of microstructure on improved mechanical properties.

scholarly journals Nano-sized BaSnO3 powder via a precursor route. Comparative study of sintering behaviour and mechanism of fine and coarse-grained powders.

2018 ◽  
Author(s):  
Roberto Köferstein
Keyword(s):  
Comparative Study ◽  
Single Crystal ◽  
Relative Density ◽  
Reference Value ◽  
Coarse Grained ◽  
Calcination Process ◽  
Precursor Route ◽  
Complex Precursor ◽  
Sintering Behaviour ◽  
Powder Compacts

Preparation of a very fine BaSnO3 powder by calcination of a barium tin 1,2-ethanediolato complex precursor and its sintering behaviour are described herein. A ratecontrolled calcination process to 820 °C leads to a nm-sized BaSnO3 powder with aspecific surface area of S = 15.1 m2/g (dav. = 55 nm). The powder has a slightly largercell parameter of a = 412.22(7) pm compared to the single crystal value, whichdecreases with increasing calcination temperature and reaches the reference value above1000 °C. The sintering behaviour is compared between fine- and coarse-grainedBaSnO3 powders. Corresponding powder compacts of the nano-sized BaSnO3 achieve arelative density of 90 % after sintering at 1600 °C for 1 h and at 1500 °C and a soakingtime of 30 h, whereas coarse-grained powder compacts reach only 80 % of the relative density at 1650 °C (10 h). Furthermore, the shrinkage mechanisms of fine and coarsegrainedpowder compacts have been investigated and are discussed.

MICROSTRUCTURES AND MECHANICAL PROPERTIES OF ULTRAFINE GRAINED Ti-47Al-2Cr (at %) ALLOY PRODUCED USING POWDER COMPACT FORGING

2009 ◽  
Vol 23 (06n07) ◽  
pp. 1739-1744
Author(s):  
VIJAY N. NADAKUDURU ◽  
DELIANG ZHANG ◽  
PENG CAO ◽  
BRIAN GABBITTAS
Keyword(s):  
Mechanical Properties ◽  
Powder Compact ◽  
High Energy ◽  
Alloy Sample ◽  
Bulk Alloy ◽  
Porosity Level ◽  
Fine Grain ◽  
Ultrafine Grained ◽  
Powder Compacts ◽  
Innovative Techniques

Development of innovative techniques to produce gamma TiAl based alloys, with good mechanical properties, while still maintaining ultra fine grain size can be rewarding, but also is a great challenge. In the present study study a Ti -47 Al -2 Cr ( at %) alloy has been synthesized by directly forging green powder compacts of a Ti / Al / Cr composite powder produced by high energy mechanical milling of a mixture of elemental Ti , Al , Cr powders. It has been found that the density of the bulk consolidated alloy sample after forging decreases from 95% of the theoretical density in the central region to 84% in the periphery region. The microstructure of the bulk alloy consisted of several Ti rich regions, which was expected to be mainly due to initial powder condition. The room temperature tensile strength of the samples produced from this process was found to be in the range of 115 – 130 MPa. The roles of canning and green powder compact density in determining the forged sample porosity level and distribution are discussed.

ChemInform Abstract: Phase Evolution During the Reactive Sintering of Ternary Al-Ni-Ti Powder Compacts.

ChemInform ◽  
2016 ◽  
Vol 47 (9) ◽  
pp. no-no
Author(s):  
Hossein Sina ◽  
Kumar Babu Surreddi ◽  
Srinivasan Iyengar
Keyword(s):  
Phase Evolution ◽  
Reactive Sintering ◽  
Ti Powder ◽  
Powder Compacts

scholarly journals Synthesis and characterization of a nano-scaled barium cerate perovskite powder using starch as polymerization agent

2018 ◽  
Author(s):  
Roberto Köferstein
Keyword(s):  
Mixed Oxide ◽  
Size Range ◽  
Phase Evolution ◽  
Coarse Grained ◽  
Synthesis And Characterization ◽  
Barium Cerate ◽  
Phase Pure ◽  
Sintering Behaviour ◽  
Powder Compacts

The preparation of nano-sized BaCeO3 powder using starch as a polymerizationagent is described herein. Phase evolution during the decomposition process of a (BaCe)-gelwas monitored by XRD. A phase-pure nano-sized BaCeO3 powder was obtained aftercalcining of the (BaCe)-gel at 920 °C. The resulting powder has a specific surface area of 15.4m2/g. TEM investigations reveal particles mainly in the size range of 30 to 65 nm. Theshrinkage and sintering behaviour of resulting powder compacts were studied in comparisonto a coarse-grained mixed-oxide BaCeO3 powder (SBET = 2.1 m2/g). Dilatometricmeasurements show that the beginning of shrinkage of compacts from the nano-sized powder is downshifted by 300 °C compared to mixed-oxide powder. Compacts from the nano-sizedpowder reach a relative density of 91 % after sintering at 1450 °C for 10 h.

Phase evolution of solid-state BaTiO3 powder prepared with the ultrafine BaCO3 and TiO2

2012 ◽  
Vol 27 (19) ◽  
pp. 2495-2502 ◽  
Author(s):  
Ting-Tai Lee ◽  
Chi-Yuen Huang ◽  
Che-Yuan Chang ◽  
I-Kuan Cheng ◽  
Ching-Li Hu ◽  
...  
Keyword(s):  
Solid State ◽  
Phase Evolution ◽  
Batio3 Powder ◽  
Image Position

Abstract

Sign in / Sign up

Export Citation Format

Share Document