scholarly journals Quantitative formulation of mechanism of sintering process during creep deformation of refractory concretes

2009 ◽  
Vol 41 (1) ◽  
pp. 49-58
Author(s):  
Anja Terzic ◽  
Lj. Pavlovic
Keyword(s):  
Creep Deformation ◽  
Static Pressure ◽  
Refractory Concrete ◽  
Sintering Process ◽  
Time Intervals ◽  
Different Temperatures ◽  
Metallurgical Furnaces ◽  
Mineralogical Compositions ◽  
Constant Static Pressure ◽  
Secondary State

This paper is concerned with quantitative formulation of the mechanism of the sintering process during secondary state creep deformation of refractory concretes. Investigated concretes varied in, both, chemical and mineralogical compositions. The sintering process during secondary state creep within refractory concrete has an isothermal character. Thus, an attempt was made to describe the mentioned process quantitatively. Creep was investigated at three different temperatures: 1200, 1300 and 1400?C. Variations of the microstructure of concrete samples, exposed to constant static pressure and constant temperature during certain time-intervals, were investigated using a scanning electron microscope. Obtained results of the investigation proved that creep resistance is an irreplaceable method when the decision about the best possible type of refractory concrete for application in metallurgical furnaces is required.

Effects of Constant Static Pressure on the Biological Properties of Porcine Aortic Valve Leaflets

2004 ◽  
Vol 32 (4) ◽  
pp. 555-562 ◽  
Author(s):  
Yun Xing ◽  
Zhaoming He ◽  
James N. Warnock ◽  
Stephen L. Hilbert ◽  
Ajit. P. Yoganathan
Keyword(s):  
Aortic Valve ◽  
Static Pressure ◽  
Biological Properties ◽  
Aortic Valve Leaflets ◽  
Constant Static Pressure

scholarly journals Is ink heating a relevant concern in the High Speed Sintering process?

2021 ◽  
Author(s):  
Rhys J. Williams ◽  
Patrick J. Smith ◽  
Candice Majewski
Keyword(s):  
Cross Sections ◽  
Inkjet Printing ◽  
High Speed ◽  
Sintering Process ◽  
Significant Drop ◽  
Powder Bed ◽  
Consistent Manner ◽  
Fluid Properties ◽  
Different Temperatures ◽  
Accuracy And Repeatability

AbstractHigh Speed Sintering (HSS) is a novel polymer additive manufacturing process which utilises inkjet printing of an infrared-absorbing pigment onto a heated polymer powder bed to create 2D cross-sections which can be selectively sintered using an infrared lamp. Understanding and improving the accuracy and repeatability of part manufacture by HSS are important, ongoing areas of research. In particular, the role of the ink is poorly understood; the inks typically used in HSS have not been optimised for it, and it is unknown whether they perform in a consistent manner in the process. Notably, the ambient temperature inside a HSS machine increases as a side effect of the sintering process, and the unintentional heating to which the ink is exposed is expected to cause changes in its fluid properties. However, neither the extent of ink heating during the HSS process nor the subsequent changes in its fluid properties have ever been investigated. Such investigation is important, since significant changes in ink properties at different temperatures would be expected to lead to inconsistent printing and subsequently variations in part accuracy and even the degree of sintering during a single build. For the first time, we have quantified the ink temperature rise caused by unintentional, ambient heating during the HSS process, and subsequently measured several of the ink’s fluid properties across the ink temperature range which is expected to be encountered in normal machine operation (25 to 45 ∘C). We observed only small changes in the ink’s density and surface tension due to this heating, but a significant drop (36%) in its viscosity was seen. By inspection of the ink’s Z number throughout printing, it is concluded that these changes would not be expected to change the manner in which droplets are delivered to the powder bed surface. In contrast, the viscosity decrease during printing is such that it is expected that the printed droplet sizes do change in a single build, which may indeed be a cause for concern with regard to the accuracy and repeatability of the inkjet printing used in HSS, and subsequently to the properties of the polymer parts obtained from the process.

scholarly journals Acid and Temperature Treatments Result in Increased Germination of Seeds of Three Fescue Species

2012 ◽  
Vol 40 (2) ◽  
pp. 220 ◽  
Author(s):  
Rade S. STANISAVLJEVIC ◽  
Savo M. VUCKOVIC ◽  
Aleksandar S. SIMIC ◽  
Jordan P. MARKOVIC ◽  
Zelijco P. LAKIC ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Seed Germination ◽  
Acid Solution ◽  
Sulfuric Acid Solution ◽  
Germination Rate ◽  
Festuca Rubra ◽  
Time Intervals ◽  
Different Temperatures ◽  
Successful Establishment ◽  
Seed Collecting

Efficient germination of fescue seeds is essential for successful establishment of meadows and pastures. This research was conducted to ascertain the effects of various acid and temperature treatments on seed germination in three fescue species: Festuca rubra, F. ovina, and F. pratensis. Seeds from different cultivars, populations, or lots were exposed either to four concentrations of sulfuric acid at three different time intervals (12 treatments) or six different temperatures at three different time intervals (18 treatments). Despite all belonging to the genus Festuca, the seed from different species responded differently to the treatments. The three optimum treatments for F. rubra seed involved soaking in a 75% solution of sulfuric acid for 20 minutes (improved the germination rate by 19%), soaking in a 50% solution of sulfuric acid for 30 minutes (improved the germination rate by 18%) and exposure to either 60°C or 70°C for 90 minutes (improved the germination rate by 17%). For F. ovina seed, optimal treatments included soaking seeds for either 10 or 20 minutes in a 50% sulfuric acid solution (both treatments improved germination rates by 13%) or exposing seeds for 30 minutes in a 25% sulfuric acid solution and 80°C for 60 minutes (improved germination rate by 12%). Two optimal treatments were identified for F. pratensis seed. Whereas the first involved soaking the seeds in a 75% sulfuric acid solution for 30 minutes (improved germination rates by 22%), the second involved either exposing the seeds to 90°C for 90 or 60 minutes, or exposing the seeds to 80°C for 90 minutes (improved germination rate by 21%). Our findings indicate that if fescue seed is to be sown during the autumn (two to three months after seed collecting), treating it with acid and temperature can significantly enhance its germination.

On an approximate model for the shape of a liquid–air interface receding in a capillary tube

1997 ◽  
Vol 342 ◽  
pp. 87-96 ◽  
Author(s):  
E. RAMÉ
Keyword(s):  
Boundary Condition ◽  
Contact Angle ◽  
Static Pressure ◽  
Capillary Tube ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Approximate Model ◽  
Viscous Stress ◽  
Air Interface ◽  
Constant Static Pressure

A good approximation to modelling the shape of a liquid–air meniscus advancing or receding in a capillary tube of radius a can be constructed by balancing the curvature of the interface with the sum of a viscous stress valid near the contact line and a constant static pressure. This model has unique solutions for each value of the boundary condition, i.e. the dynamic contact angle. When the meniscus recedes at very small capillary numbers, the model predicts a critical receding velocity beyond which a liquid layer of the receding fluid (a liquid tail) develops along the solid (see figure 4). The length of the layer increases as the receding speed and the contact angle decrease. This layer regime is characterized by menisci whose macroscopic curvature is >1/a.

scholarly journals Formation of irregular rings in silica aerogel structure during the sintering process

2003 ◽  
Vol 35 (2) ◽  
pp. 67-73
Author(s):  
Ivana Hinic ◽  
Goran Stanisic ◽  
Zoran Popovic
Keyword(s):  
Raman Spectroscopy ◽  
Bulk Density ◽  
Raman Spectra ◽  
Silica Aerogel ◽  
Structural Changes ◽  
Low Density ◽  
Sintering Process ◽  
Time Intervals ◽  
Defect Modes

Samples of low-density, highly disordered silica aerogel with initial bulk density of 0.16 g/cm3, were sintered isothermally in different time intervals at 1000?C. Structural changes during the sintering process have been investigated by Raman spectroscopy. Defect modes of irregular three and four membered rings were observed in the Raman spectra of sintered samples.

scholarly journals STABILITY STUDY OF AMLODIPINE BESYLATE AND BISOPROLOL FUMARATE IN AQUEOUS SOLUTIONS

2014 ◽  
Vol 5 (2) ◽  
Author(s):  
Irena Kasagić Vujanović ◽  
Dijana Jelić ◽  
Vesna Antunović ◽  
Biljana Jančić Stojanović ◽  
Darko Ivanović
Keyword(s):  
Relevant Information ◽  
Pharmaceutical Product ◽  
Stability Study ◽  
Amlodipine Besylate ◽  
Time Intervals ◽  
Constant Rate ◽  
Different Temperatures ◽  
The Media ◽  
Two Temperatures ◽  
The Stability

Valuable information concerning stability of compounds can be obtained by using different media (water, hydrochloric acid or sodium hydroxide) for dissolution of active pharmaceutical substances. Furthermore, additional knowledge is gained by performing experiments at different temperatures. This research paper deals with the stability of amlodipine besylate and bisoprolol fumarate in different media at different temperatures, whereby certain conclusions are drawn. For stability assessment, chemical kinetics approach was used, and constant rate (k), half-time (t1/2) and activation energy (Ea) were used for prediction of compound stability degree. The stability of amlodipine besylate and bisoprolol fumarate were tested, both separately and in mixture, in water and in 0.01M HCl. All the investigated solutions were treated at two temperatures 25° and 70°C at the following time intervals: 0, 1 h, 24 h, 48 h and 72 h. Hydrophilic Interaction Liquid Chromatography – HILIC method, previously developed and validated, was used. On the basis of obtained results it was concluded that amlodipine-besylate was more stable in water than in acid medium, more stable in mixture rather than individually and more stable at lower temperatures. This was confirmed by the obtained values of monitored parameters: amlodipine besylate Ea = 30.68 kJ mol-1, k (25 °C) = 0.000333 mM h-1, k (70 °C) = 0.00169 mM h-1; amlodipine besylate in mixture Ea = 42,414 kJ mol-1, k (25 °C) = 1.27∙10-4 mM h-1, k (70 °C) = 0.0012 mM h-1. Based on the obtained approximate Ea value for bisoprolol fumarate in acid (59 kJ mol-1) and in water (56 kJ mol-1), bisoprolol fumarate showed excellent stability against the media in which it was studied. On the other hand, the temperature had a significant effect on the stability of bisoprolol fumarate. These results provide the relevant information about the stability of the tested active substances, and may be of importance during the development of an appropriate pharmaceutical product. A bigger influence on the stability of bisoprolol fumarate had a temperature effect.

scholarly journals Effects of oxidation of SiC aggregates on the sintering behaviour and microstructures of SiC-CaAl12O19 composite refractories

2021 ◽  
Vol 15 (1) ◽  
pp. 11-18
Author(s):  
Yaochen Si ◽  
Miao Xia ◽  
Hongxia Li ◽  
Honggang Sun ◽  
Ang Guo ◽  
...  
Keyword(s):  
Firing Temperature ◽  
Sintering Temperature ◽  
Raw Materials ◽  
Coal Slurry ◽  
Refractory Materials ◽  
Sintering Process ◽  
Active Oxidation ◽  
Passive Oxidation ◽  
Different Temperatures ◽  
Sintering Behaviour

In order to develop chrome-free refractory materials applicable in coal slurry gasification, SiC-CaAl12O19 (SiC-CA6) composite refractories were developed and prepared by using SiC aggregates and CA6 powders as main raw materials. The sintering behaviour of the composites was investigated. After firing at different temperatures under CO atmosphere, the effects of oxidation of SiC aggregates on the sintering behaviour and microstructures of SiC-CA6 composite refractorieswere investigated. SiC-CA6 composites could not be sintered when firing temperature was lower than 1500?C. SiC had a passive oxidation and the oxidation components were able to react with CA6 to form CaAl2Si2O8. The CaAl2Si2O8 melted into liquid when sintering temperature was in the range of 1500-1600?C, which promoted the sintering process of the SiC-CA6 composites. At temperatures above 1600 ?C, an active oxidation of SiC occurred. Simultaneously, SiC could also reacted with the SiO2(s,l) to form SiO, leading to the precipitation of Al2O3 and CaO in the liquid to generate plate-like CA6. Above this temperature, the sintering of the SiC-CA6 composite refractories was affected by the growth of CA6 and oxidation of SiC. This work demonstrates that the optimal sintering temperature for the SiC-CA6 composite refractories was 1600?C.

The Pressure Registered by a Very Small Static Hole

1961 ◽  
Vol 65 (611) ◽  
pp. 766-767 ◽  
Author(s):  
J. D. Jackson
Keyword(s):  
Static Pressure ◽  
Fundamental Importance ◽  
Hole Size ◽  
Extrapolation Procedure ◽  
True Value ◽  
Moving Fluid ◽  
Constant Static Pressure

Static pressure in a moving fluid is usually measured by means of a static hole either in a probe or on the wall of a duct. Such a hole creates a disturbance in the flow and thus has some error associated with it. The determination of the magnitude of this error has been attempted by several investigators and the procedure adopted in each case has been as follows :The pressure in a region of sensibly constant static pressure was registered using holes of various diameter and a curve of pressure versus hole size plotted. The true static pressure was then obtained by extrapolating this curve to zero hole size, and the errors for the various holes were found. This procedure involves the assumption that, as the hole size tends to zero, the pressure registered tends to the true value. It is usually argued that this must be so because the disturbance caused by the static hole is progressively reduced as the hole size is reduced. Obviously, the validity, or otherwise, of the argument is of fundamental importance in the estimation of static hole error, and a somewhat more rigorous justification of the use of the extrapolation procedure is attempted in what follows.

Quantitative Analysis of Intermetallic Precipitates in High Mo Superaustenitic Stainless Steel

2014 ◽  
Vol 592-594 ◽  
pp. 711-715
Author(s):  
J. Anburaj ◽  
S.S. Mohamed Nazirudeen ◽  
K. Thillairajan ◽  
A. Chandrasekar ◽  
R Narayanan
Keyword(s):  
Stainless Steel ◽  
Quantitative Analysis ◽  
Ageing Time ◽  
Intermetallic Phases ◽  
Superaustenitic Stainless Steel ◽  
Time Intervals ◽  
Intermetallic Precipitates ◽  
Thermo Calc Software ◽  
Different Temperatures ◽  
Mo Content

Influence of ageing temperatures and ageing time intervals on the intermetallic phases of high Mo superaustenitic stainless steel (SASS) is studied. To form the intermetallic phases the alloy was aged for 1 hour and 10 hours at different temperatures in the range of 500-1000°C. Chi forms at temperatures up to 800°C. Sigma forms above 900 or 1000°C depending upon the ageing time. A property diagram is simulated using Thermo-calc software to corroborate the formation of chi and sigma phases as a function of ageing temperatures. EDS of sigma indicated its higher Mo content compared to the chi phase. Chi is enriched in chromium while sigma is enriched in Mo.

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