Rapid Consolidation of Nanophase Al2O3 and an Al2O3/Al2TiO5 Composite

1996 ◽  
Vol 457 ◽  
Author(s):  
David A. West ◽  
Rajiv S. Mishra ◽  
Amiya K. Mukherjee
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Powder Compact ◽  
Single Phase ◽  
Rapid Heating ◽  
Resistance Heating ◽  
Sintering Process ◽  
Heating Rates ◽  
Dc Voltage ◽  
Rapid Heating Rate

ABSTRACTA rapid consolidation technique has been utilized in producing single phase AI2O3 in less than 10 minutes at 1400°C resulting in a grain size less than 500 nm. TiO2 has been added in hopes of obtaining Al2O3/Al2TiO5 nanocomposites in sintering times less than 30 minutes. The sintering process involves resistance heating of a graphite die containing the powder at heating rates of about 10 °C/s. The resistance heating step is preceded by a preparatory step consisting of DC voltage pulses applied across a prepressed powder compact. The retention of the nanostructure is attributed to the rapid heating rate although the possible effect of the DC pulses are also discussed. An Al2O3/Al2TiO5 composite has been produced during a short anneal immediately following sintering of an Al2O3/TiO2 nanocomposite. Substantial grain growth has been observed to occur during the transformation taking the composite to the microcrystalline regime.

Microwave sintering of ZnO at ultra high heating rates

2001 ◽  
Vol 16 (10) ◽  
pp. 2850-2858 ◽  
Author(s):  
Geng-fu Xu ◽  
Isabel K. Lloyd ◽  
Yuval Carmel ◽  
Tayo Olorunyolemi ◽  
Otto C. Wilson
Keyword(s):  
Grain Size ◽  
Heating Rate ◽  
Microwave Heating ◽  
Grain Growth ◽  
Rapid Heating ◽  
Microwave Sintering ◽  
Complete Suppression ◽  
Heating Rates ◽  
High Heating ◽  
Size Uniformity

In this paper, a unique processing approach for producing a tailored, externally controlled microstructure in zinc oxide using very high heating rates (to 4900 °C/min) in a microwave environment is discussed. Detailed data on the densification, grain growth, and grain size uniformity as a function of heating rate are presented. With increasing heating rate, the grain size decreased while grain size uniformity increased. At extremely high heating rates, high density can be achieved with almost complete suppression of grain growth. Ultrarapid microwave heating of ZnO also enhanced densification rates by up to 4 orders of magnitude compared to slow microwave heating. The results indicate that the densification mechanisms are different for slow and rapid heating rates. Since the mechanical, thermal, dielectric, and optical properties of ceramics depend on microstructure, ultrarapid heating may lead to advanced ceramics with tailored microstructure and enhanced properties.

Modeling the Densification of FeSi Sintered Magnetic Alloys

2012 ◽  
Vol 727-728 ◽  
pp. 175-180 ◽  
Author(s):  
José Adilson de Castro ◽  
Gilberto V. Concilio ◽  
Daniel Rodrigues ◽  
Livia S. Santomauro ◽  
Marcos Flavio de Campos
Keyword(s):  
Experimental Data ◽  
Grain Size ◽  
Sintering Temperature ◽  
Process Parameter ◽  
Model Parameters ◽  
Important Process ◽  
Sintering Process ◽  
Heating Rates ◽  
Magnetic Alloys ◽  
Sintered Alloys

An important process parameter in FeSi sintered alloys is the sintering temperature. If the sintering temperature can be reduced, the sintering process could be performed in less expensive furnaces. A densification model is here applied to experimental data. The model considers both grain size and density. After the model is applied to experimental data, the acquired model parameters allow the simulation of densification for other situations of temperature and heating rates. The model can be helpful to find suitable sintering temperatures in these alloys.

Nanostructure Evolution of ZnO in Ultra-fast Microwave Sintering

2011 ◽  
Vol 691 ◽  
pp. 65-71 ◽  
Author(s):  
Rodolfo F. K. Gunnewiek ◽  
Ruth Herta Goldsmith Aliaga Kiminami
Keyword(s):  
Grain Size ◽  
Zinc Oxide ◽  
Grain Growth ◽  
Microwave Sintering ◽  
High Heating Rate ◽  
Heating Rates ◽  
Grain Sizes ◽  
Average Grain Size ◽  
Conventional Sintering ◽  
Holding Temperature

Grain growth is inevitable in the sintering of pure nanopowder zinc oxide. Sintering depend on diffusion kinetics, thus this growth could be controlled by ultra-fast sintering techniques, as microwave sintering. The purpose of this work was to investigate the nanostructural evolution of zinc oxide nanopowder compacts (average grain size of 80 nm) subjected to ultra-rapid microwave sintering at a constant holding temperature of 900°C, applying different heating rates and temperature holding times. Fine dense microstructures were obtained, with controlled grain growth (grain size from 200 to 450nm at high heating rate) when compared to those obtained by conventional sintering (grain size around 1.13µm), which leads to excessively large average final grain sizes.

Two-Steps Sintering of Alumina-Zirconia Ceramics

2010 ◽  
Vol 660-661 ◽  
pp. 819-825
Author(s):  
Milena K. Manosso ◽  
Elíria Maria Jesus Agnolon Pallone ◽  
Adilson Luiz Chinelatto ◽  
Adriana Scoton Antonio Chinelatto
Keyword(s):  
Grain Size ◽  
Ball Milling ◽  
Grain Growth ◽  
Sintering Process ◽  
Ceramic Powders ◽  
Zirconia Ceramics ◽  
Linear Rate ◽  
Commercial Alumina ◽  
Mean Grain Size ◽  
Cold Pressed

Sintering in two-steps has been applied with success for densification of nanometric ceramic powders without grain growth. Another mechanism that alters the sintering process is the presence of rigid inclusions in the ceramic. In this work it was studied the effect of two-steps sintering and the presence of zirconia inclusions (5% in volume) in the microstructure of a commercial alumina. For this, the powders of alumina and zirconia were desaglomerated in a ball milling and uniaxially pressed at 80 MPa to form cylindrical compacts and isostatically cold pressed at 200 MPa. Temperatures of the steps were chosen starting from the curves of linear rate shrinkage in function of the temperature. The samples were characterized for apparent density, scanning electronic microscopic and mean grain size. The results showed that two-steps sintering and the zirconia inclusions were efficient to control the densification and grain size of alumina.

Influence of Heating Rate and Decarburization Temperature on the Microstructure and Magnetic Properties of Grain Oriented Electrical Steel

2012 ◽  
Vol 706-709 ◽  
pp. 2622-2627 ◽  
Author(s):  
Chun Kan Hou ◽  
Jian Ming Tzeng
Keyword(s):  
Magnetic Properties ◽  
Heating Rate ◽  
Grain Growth ◽  
Electrical Steel ◽  
Rapid Heating ◽  
Abnormal Grain Growth ◽  
Heating Rates ◽  
Abnormal Growth ◽  
Steel Sheets ◽  
Microstructure And Magnetic Properties

Effects of three heating rates, 5, 20/min., and 300°C/sec and decarburization temperature, 700-850°C in primary annealing on the microstructure and magnetic properties of a grain oriented electrical steel were investigated. It was found that the oxide layer thickness and grain size increased with increasing decarburization temperature. However, they decreased with increasing heating rate. On the other hand, injection nitrogen content into steel sheets decreased with increasing decarburization temperature. The percentage of abnormal grain growth obtained a peak value at 800°C in the specimens treated with heating rate less than 20°C per minute. But specimens with rapid heating rate, percentage of abnormal grain growth increased with increasing decarburization temperature. As percentage of abnormal growth increased, magnetic properties got better.

The Effect of Final Annealing Heating Rate on Abnormal Grain Growth in a Fe-3.5%Si Steel

2016 ◽  
Vol 879 ◽  
pp. 350-355
Author(s):  
Fatayalkadri Citrawati ◽  
Md Zakaria Quadir ◽  
Paul Munroe
Keyword(s):  
Grain Size ◽  
Heating Rate ◽  
Grain Growth ◽  
Growth Kinetics ◽  
Annealing Time ◽  
Annealing Temperature ◽  
Rapid Heating ◽  
Secondary Recrystallization ◽  
Recrystallization Annealing ◽  
Final Annealing

In this study the effects of heating rate on the sharpness and size of Goss oriented ({110}<001>) grains during secondary recrystallization annealing at 900 °C was observed. The results show that, at the same annealing temperature, rapid heating of the samples to this temperature generates a higher drag force compared to a slower heating rate (5°C/min). The two groups of samples show different growth kinetics for Goss grains, in which at the longest annealing time, the rapid heating sample exhibits larger maximum Goss grain size compared to the slower heated samples.

Microstructural Evolution and Quenching Properties of 22MnB5 Steel for Hot Stamping during Resistance Heating

2013 ◽  
Vol 849 ◽  
pp. 75-80 ◽  
Author(s):  
Cai Na Sun ◽  
Heng Hua Zhang
Keyword(s):  
Grain Size ◽  
Tensile Strength ◽  
Microstructural Evolution ◽  
Continuous Heating ◽  
Resistance Heating ◽  
Heating Rates ◽  
Austenite Grain Size ◽  
Furnace Heating ◽  
22Mnb5 Steel ◽  
Austenite Grain

Austenitic continuous heating transformation dynamics, microstructural evolution and quenching properties of 22MnB5 steel during resistance heating were investigated. Steel sheets with thickness of 1.6 mm were heated to various temperatures (800~1200 °C) either by resistance heating at two heating rates of 100 and 300 °C/s or furnace heating. The increment of superheat degree was parabolic relationship with increasing heating rate. Samples heated above Ac3 of respective heating rates exhibited a full martensite microstructure and a hardness of above 490 HV. Austenitic coarsening rate of resistance heating samples was much lower than those by furnace heating. Austenite grain size by resistance heating was smaller than 38 μm while these by furnace heating reached 74 μm at 1200 °C. Samples heated by resistance heating at 300 °C/s had a good performance of 1800 MPa tensile strength and 5.6 % elongation, and product of strength and elongation reaches 10080 MPa%. The good combination of tensile strength and elongation by resistance heating might result from the finer austenite grain size and smaller martensite plate.

Simulation of the Effect of Sintering Pressure on Microstructure Evolution in Nanocomposite Ceramic Tool Materials

2013 ◽  
Vol 395-396 ◽  
pp. 262-265 ◽  
Author(s):  
Hong Mei Cheng ◽  
Chuan Zhen Huang
Keyword(s):  
Grain Size ◽  
Monte Carlo ◽  
Grain Growth ◽  
Microstructure Evolution ◽  
Growth Process ◽  
Sintering Process ◽  
Ceramic Tool ◽  
Tool Materials ◽  
Mean Grain Size ◽  
The Mean

A Monte Carlo Potts model coupled with sintering pressure for the sintering process of nanocomposite ceramic tool materials is proposed, the relation between grain growth and sintering pressure is presented. The grain growth process at different sintering pressure is investigated in this model, and the effect of sintering pressure on microstructure evolution is discussed, it is found that the mean grain size increases with the increase of sintering pressure during simulation. The results from this simulation are shown to correlate well with the experimental observations.

Relationships between Processing Parameters and Properties of PZT Ceramics

2008 ◽  
Vol 55-57 ◽  
pp. 57-60
Author(s):  
C. Puchmark ◽  
Gobwute Rujijanagul
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Lead Zirconate Titanate ◽  
Sintering Temperature ◽  
Processing Parameters ◽  
Lead Zirconate ◽  
Growth Equation ◽  
Sintering Process ◽  
Pzt Ceramics ◽  
Linear Fit

In present work, lead zirconate titanate (PZT) ceramics, having the composition near morphotropic phase boundary were prepared by conventional mixed oxide method. The sintering process was performed at various sintering temperatures ranging from 1100 to 1300 oC. Relationships between phase and sintering temperature, and phase and structure were reported. An increase sintering temperature affected the increase in grain size. The grain growth rate was found to have a linear fit with the phenomenological kinetic grain growth equation. Tetragonal relative fraction increased with increasing sintering temperature. In addition, dielectric constant at dielectric peak increased with increasing grain size which consistent with the trend of tetragonality.

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