Rate Controlled Sintering Revisited

Palmour, Hayne; Hare, T. M.

doi:10.1007/978-1-4613-2851-3_2

Cited by 26 publications

(7 citation statements)

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“…To keep the shrinkage rate constant, it is necessary to increase the rate of temperature rise in the final sintering stage. Palmour et al pointed out the difficulty to keep up with the heating rate of the furnace temperature in the final sintering stage, [19][20] where the shrinkage rate is observed to decrease significantly, owing to the poor response of furnace temperature against input power. In contrast, the SCF heats a green compact directly using an electric power input.…”

Section: Resultsmentioning

confidence: 99%

“…As a control technique for the shrinkage behavior, a rate-control technique has been reported for conventional thermal sintering without electric fields by several workers. [19][20][21][22][23] The rate-control technique involves a constant shrinkage rate during the heating process by controlling the heating rate of the furnace temperature. Studies empirically suggest that the shrinkage is enhanced and the grain size is decreased effectively compared with those obtained by conventional thermal sintering.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, this study was conducted to control the current during flash sintering from the viewpoint of controlling the shrinkage behavior. As a control technique for the shrinkage behavior, a rate‐control technique has been reported for conventional thermal sintering without electric fields by several workers 19–23 . The rate‐control technique involves a constant shrinkage rate during the heating process by controlling the heating rate of the furnace temperature.…”

Section: Introductionmentioning

confidence: 99%

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Shrinkage rate control during a flash state by current‐ramping for 3 mol% Y₂O₃‐doped ZrO₂ polycrystals

et al. 2021

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3 mol% Y 2 O 3 -doped ZrO 2 green compacts with rectangular shapes were sintered by maintaining the shrinkage rates at constant values under alternating electric fields by ramping the electric current during flash states. Green compacts were furnace-heated under 40-100 V rms /cm until current hits an initial current limit of 100 mA rms . After then, current-ramping was started to keep the shrinkage rates constant by increasing the limit current value using a programmable power supply operating in a current control mode. Highly densified 3 mol% Y 2 O 3 -doped ZrO 2 polycrystals with a density of 6.05 g/cm 3 as a bulk density and a grain size of about 0.4 μm were obtained at a furnace temperature of about 930℃, 50 V rms /cm with 1000 Hz and shrinkage rate of about 120 μm/min (0.8%/min against initial lengths of green compacts). The Vickers hardness and indentation fracture toughness of the compact exhibit similar values to those obtained from thermally sintered compacts.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Shrinkage rate control during a flash state by current‐ramping for 3 mol% Y₂O₃‐doped ZrO₂ polycrystals

et al. 2021

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“…22 In addition to common ramp and hold schedules, numerous pressureless sintering methods using conventional furnaces have been mentioned in the literature. One of the earliest attempts to optimise firing schedules was the Rate-Controlled Sintering (RCS), 23 which uses the monitoring of densification to establish the heating schedules. The main approach of RCS is to maintain the pore channels open by extending the intermediate stage of sintering so that grain growth can be effectively hindered and pore removal through grain boundary can continue up to values of 90% Theoretical Density (TD).…”

Section: Introductionmentioning

confidence: 99%

Obtaining highly dense YSZ nanoceramics by pressureless, unassisted sintering

Hotza

García

Castro

2015

International Materials Reviews

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For technological applications, zirconia is commonly blended with other oxides to stabilise the tetragonal and/or cubic phases at low temperature, being yttria the most frequently added dopant. It is generally desirable to obtain highly dense ceramics while maintaining grain sizes in the nanoscale (,100 nm). Small grains contribute to stabilise the tetragonal phase and to improve the toughness and flexural strength. Moreover, a higher ionic conductivity for cubic zirconia electrolytes is achieved with smaller grain size and lower thickness of the intergranular regions. The sintering onset temperatures required for nanometric particles are significantly reduced when compared to conventional micrometric powders. However, densification is generally accompanied by an undesirable grain coarsening. A Ramp and Hold Sintering (RHS) is the simplest densification schedule, consisting of heating up to the peak temperature followed by a holding time at that temperature. Another approach, called Two-Step Sintering (TSS) is based on the principle that the activation energy for grain growth is lower than the activation energy of densification. The key elements in this method are heating up to a high temperature to achieve a density .75% Theoretical Density (TD) to render the pores unstable, and then cooling down rapidly to a lower temperature to finish sintering and hinder grain growth. Alternatively, considerable efforts have been made in increasing the heating rate and/or reducing the hold time at the peak temperature during sintering cycles in processes that are generally referred to as 'Fast Firing' (FF) or 'rapid sintering'. This review summarises the attempts in the literature for obtaining dense monolithic nanocrystalline Yttria-Stabilized Zirconia (YSZ) ceramics by pressureless sintering schedules carried out in conventional furnaces. RHS, FF and TSS schedules are reported only from YSZ as starting powders, i.e. without the aid of any additional dopant or grain growth inhibitor. For the sake of comparison, the discussion is focused mainly on YSZ nanoceramics with final densities .99% TD and average grain size ,100 nm. Powder and shaping effects on microstructure and properties of bulk nanoceramics are discussed. A comparison among sintering approaches is then made taking into account the microstructural development of the nanostructures and some key properties of the products.

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“…Rate controlled sintering was first proposed as a method for densifying ceramic materials [1][2][3]. In this process, furnace power is changed as instructed by a feedback control algorithm to maintain a desired shrinkage rate.…”

Section: Introductionmentioning

confidence: 99%

A novel programmed shrinkage dilatometer for optimized sintering of powder ceramics

Agarwal

Speyer

Hackenberger

1997

Journal of Thermal Analysis

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A fast-firing shrinkage rate controlled dilatometer was developed as a tool for optimizing sintering of powder compacts. The instrument described in this work features an infrared imaging radiation furnace and a low thermal mass dilatometer assembly which allowed controlled heating and cooling rates of up to 500"C min -~. Shrinkage control was accomplished using a computer interfaced PID control algorithm. Adjustments were made to hardware and software which reduced specimen creep under dilatometer pushrod load, eliminated non-uniform pushrod expansion, fostered reproducible specimen temperature determination, accounted for thermal expansion during sintering, and generated instantaneous termination of sintering at the specified end of RCS. Tests performed on ZnO samples demonstrated very rapid thermal response and excellent shrinkage control.

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Rate Controlled Sintering Revisited

Cited by 26 publications

References 5 publications

Shrinkage rate control during a flash state by current‐ramping for 3 mol% Y₂O₃‐doped ZrO₂ polycrystals

Shrinkage rate control during a flash state by current‐ramping for 3 mol% Y₂O₃‐doped ZrO₂ polycrystals

Obtaining highly dense YSZ nanoceramics by pressureless, unassisted sintering

A novel programmed shrinkage dilatometer for optimized sintering of powder ceramics

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Rate Controlled Sintering Revisited

Cited by 26 publications

References 5 publications

Shrinkage rate control during a flash state by current‐ramping for 3 mol% Y2O3‐doped ZrO2 polycrystals

Shrinkage rate control during a flash state by current‐ramping for 3 mol% Y2O3‐doped ZrO2 polycrystals

Obtaining highly dense YSZ nanoceramics by pressureless, unassisted sintering

A novel programmed shrinkage dilatometer for optimized sintering of powder ceramics

Contact Info

Product

Resources

About

Shrinkage rate control during a flash state by current‐ramping for 3 mol% Y₂O₃‐doped ZrO₂ polycrystals

Shrinkage rate control during a flash state by current‐ramping for 3 mol% Y₂O₃‐doped ZrO₂ polycrystals