An Investigation on the Mechanism of TiC+Al2O3 Formation in the Combustion Synthesis of the Mechanically Activated TiO2-Al-C System

2008 ◽  
Vol 273-276 ◽  
pp. 204-209
Author(s):  
Sayed Hamid Reza Fatemi Nayeri ◽  
Jalil Vahdati Khaki ◽  
Mohammad Reza Aboutalebi
Keyword(s):  
Combustion Synthesis ◽  
Powder Mixture ◽  
Titanium Aluminides ◽  
Milled Powder ◽  
Xrd Analysis ◽  
Single Step ◽  
Second Step ◽  
Particle Diffusion ◽  
Different Temperatures ◽  
Three Stages

A mechanism for the combustion synthesis of TiC+Al2O3 was proposed in a mechanically activated TiO2-Al-C system. As-milled powder mixture was analyzed using XRD and TEM techniques where no chemical reaction and/or inter-particle diffusion were identified. The results obtained from DTA tests on unmilled powder revealed that the combustion synthesis occurred in a single step at 962 °C while the synthesis of mechanically activated powder mixture occurred in three different stages. The XRD analysis on the synthesized samples of 8 hour premilled powder at different temperatures showed that the three stages were as follows: First the reaction between Al and TiO2 takes place forming Al3Ti, Ti2O3, and Al2O3 at 700 °C. In the second step, Ti-rich titanium aluminides (AlTi, AlTi2, and AlTi3) and TiO, are formed at 923 °C, and finally the formation of TiC+Al2O3 is completed at 1329 °C.

scholarly journals Calcium titanate ceramics obtained by combustion synthesis and two-step sintering

2020 ◽  
Vol 52 (4) ◽  
pp. 491-502
Author(s):  
Kanchana Maitreekeaw ◽  
Tawat Chanadee
Keyword(s):  
Dielectric Constant ◽  
Combustion Synthesis ◽  
Xrd Analysis ◽  
Calcium Titanate ◽  
Single Step ◽  
Dielectric Constants ◽  
Sintered Ceramic ◽  
Relaxation Polarization ◽  
Titanate Ceramics ◽  
Titanate Ceramic

Calcium titanate powder was successfully prepared from duck eggshell and anatase titanium dioxide with a magnesium inductant via combustion synthesis in argon. As-combusted products were leached with diluted HCl. In XRD analysis, as-leached powders exhibited a major phase of CaTiO3 with a perovskite structure. The particle size, observed by SEM, was approximately 240 nm. As-leached powders were densified by single-step (SST) and two-step sintering (TSS) to produce calcium titanate ceramics. The first step of all TSS conditions was fixed at 1350C and holding times (t1) at this temperature were varied up to 120 min. Calcium titanate ceramic obtained from holding for 120 min had a grain size of 2.18 ?m, relative density of 86.68% and a dielectric constant of 92. Two-step sintered ceramic had the highest density (95.73%) and best dielectric properties (dielectric constant = 110, dielectric loss = 0.02) when the holding temperature (T2) was 1250?C. Calcium titanate ceramics processed by two-step sintering had denser microstructures and higher dielectric constants than single-step sintered ceramic due to grain boundary diffusion and the simplicity of relaxation polarization.

Phase Studies in WC-Stainless Steel AISI 347 Hardmetal System with Graphite Addition

2014 ◽  
Vol 1024 ◽  
pp. 239-242
Author(s):  
Zuhailawati Hussain ◽  
Emee Marina Salleh ◽  
Tran Bao Trung ◽  
Zainal Arifin Ahmad
Keyword(s):  
Stainless Steel ◽  
Powder Mixture ◽  
Milled Powder ◽  
Graphite Powder ◽  
Planetary Mill ◽  
Argon Atmosphere ◽  
Maximum Hardness ◽  
Steel Container ◽  
Steel Aisi ◽  
Stainless Steel Aisi

In this study, WC-stainless steel AISI 347 hardmetal system was produced to replace WC-Co hardmetal which uses the expensive, toxic and depleted resource Co. WC, stainless steel AISI 347 and graphite powder mixture were milled in a planetary mill under argon atmosphere using a stainless steel container and balls. Carbon was added in amounts ranging from 0 wt% until 4 wt% into the composition to avoid unwanted η (Fe3W3C) phase. As-milled powder was compacted at 300 MPa and sintered in a tube furnace at 1350°C. ɳ phase was detected in compositions with 0 and 1 wt% C addition. For 2 wt% C addition, no η (Fe3W3C) phase formation was identified. However, the η phase was detected for compositions containing 3 and 4 wt% C. Maximum hardness was achieved due to the absence of η phase.

scholarly journals A Logistic Approach for Kinetics of Isothermal Pyrolysis of Cellulose

Processes ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 551
Author(s):  
Jorge López-Beceiro ◽  
Ana María Díaz-Díaz ◽  
Ana Álvarez-García ◽  
Javier Tarrío-Saavedra ◽  
Salvador Naya ◽  
...  
Keyword(s):  
Kinetic Model ◽  
Time Derivative ◽  
Inert Atmosphere ◽  
Second Step ◽  
Rate Parameter ◽  
Thermogravimetric Data ◽  
Different Temperatures ◽  
Parameter Values ◽  
Kinetics Of ◽  
Logistic Functions

A kinetic model is proposed to fit isothermal thermogravimetric data obtained from cellulose in an inert atmosphere at different temperatures. The method used here to evaluate the model involves two steps: (1) fitting of single time-derivative thermogravimetric curves (DTG) obtained at different temperatures versus time, and (2) fitting of the rate parameter values obtained at different temperatures versus temperature. The first step makes use of derivative of logistic functions. For the second step, the dependence of the rate factor on temperature is evaluated. That separation of the curve fitting from the analysis of the rate factor resulted to be very flexible since it proved to work for previous crystallization studies and now for thermal degradation of cellulose.

CHARACTERIZATION OF HYDROXYAPATITE/TI6AL4V COMPOSITE POWDER UNDER VARIOUS SINTERING TEMPERATURE

2015 ◽  
Vol 75 (7) ◽  
Author(s):  
Amir Arifin ◽  
Abu Bakar Sulong ◽  
Norhamidi Muhamad ◽  
Junaidi Syarif
Keyword(s):  
Mechanical Properties ◽  
Composite Powder ◽  
Sintering Temperature ◽  
Physical And Mechanical Properties ◽  
Xrd Analysis ◽  
X Ray Diffraction ◽  
Different Temperatures ◽  
Two Phases ◽  
Work Interaction

Hydroxyapatite (HA) has been widely used in biomedical applications due to its excellent biocompatibility. However, Hydroxyapatite possesses poor mechanical properties and only tolerate limited loads for implants. Titanium is well-known materials applied in implant that has advantage in mechanical properties but poor in biocompatibility. The combination of the Titanium alloy and HA is expected to produce bio-implants with good in term of mechanical properties and biocompatabilty. In this work, interaction and mechanical properties of HA/Ti6Al4V was analyzed. The physical and mechanical properties of HA/Ti6Al4V composite powder obtained from compaction (powder metallurgy) of 60 wt.% Ti6Al4V and 40 wt.% HA and sintering at different temperatures in air were investigated in this study. Interactions of the mixed powders were investigated using X-ray diffraction. The hardness and density of the HA/Ti6Al4V composites were also measured. Based on the results of XRD analysis, the oxidation of Ti began at 700 °C. At 1000 °C, two phases were formed (i.e., TiO2 and CaTiO3). The results showed that the hardness HA/Ti6Al4V composites increased by 221.6% with increasing sintering temperature from 700oC to 1000oC. In contrast, the density of the composites decreased by 1.9% with increasing sintering temperature. 

Flameless Solution Combustion Synthesis of Al3+ Doped LiMn2O4

2011 ◽  
Vol 186 ◽  
pp. 7-10 ◽  
Author(s):  
Gui Yang Liu ◽  
Jun Ming Guo ◽  
Bao Sen Wang ◽  
Ying He
Keyword(s):  
Combustion Synthesis ◽  
Synthesis Method ◽  
Solution Combustion Synthesis ◽  
Xrd Analysis ◽  
Cycling Performance ◽  
X Ray Diffraction ◽  
Solution Combustion ◽  
Electrochemical Test ◽  
Micro Morphology ◽  
Better Than

Single phase Al3+ doped LiMn2O4 has been prepared by flameless solution combustion synthesis method at 600oC for 1h. X-ray diffraction (XRD) and scanning electric microscope (SEM) were used to determine the phase composition and micro morphology of the products. XRD analysis indicates that the purities increase and the lattice parameters of the products decrease with increasing Al3+ content. Electrochemical test indicates that the cycling performance of the products with Al3+ doping are better than that of the product without Al3+ doping. The product LiAl0.10Mn1.90O4 gets the best electrochemical performance. At the current density of 30mA/g, the initial discharge capacity of LiAl0.10Mn1.90O4 is 124.8mAh/g, and after 20 cycles, the capacity retention is more than 89%. SEM investigation indicates that the particles of LiAl0.10Mn1.90O4 are sub-micron in size and well dispersed.

An efficient solution for the single-step synthesis of 4CaO·Al2O3·Fe2O3 powders

2009 ◽  
Vol 24 (1) ◽  
pp. 245-252 ◽  
Author(s):  
Robert Ianoş
Keyword(s):  
Combustion Synthesis ◽  
Solution Combustion Synthesis ◽  
Cost Effective ◽  
Fuel Mixture ◽  
Single Step ◽  
Combustion Reaction ◽  
Exothermic Effect ◽  
Solution Combustion ◽  
Time Saving ◽  
X Ray

Single-phase nanocrystalline 4CaO·Al2O3·Fe2O3 powders were prepared directly from the combustion reaction using a new cost-effective, time-saving, and environmentally friendly version of solution combustion synthesis. Instead of a single fuel, a fuel mixture of urea and β-alanine was used. It was shown by x-ray diffraction, energy-dispersive x-ray analysis, thermogravimetric analysis, and optical microscopy that this new version of the solution combustion synthesis allows the maximization of the exothermic effect associated with the combustion reaction. On the other hand, it was shown that the traditional version of combustion synthesis involving the use of a single fuel, such as urea or β-alanine, does not ensure the formation of Ca4Al2Fe2O10 unless subsequent thermal treatments are applied. It was suggested that the occurrence of combustion reactions cannot be regarded only in terms of adiabatic temperature, as the kinetic aspects overrule the thermodynamic ones.

The Reactivity of CaTi4(PO4)6 with Alumina and Y-TZP Ceramics

2007 ◽  
Vol 361-363 ◽  
pp. 787-790
Author(s):  
Sabina Beranič Klopčič ◽  
Irena Pribošič ◽  
Tomaž Kosmač ◽  
Ute Ploska ◽  
Georg Berger
Keyword(s):  
Room Temperature ◽  
Xrd Analysis ◽  
Second Phase ◽  
Reaction Products ◽  
Stabilized Zirconia ◽  
Monoclinic Zro2 ◽  
Commercial Alumina ◽  
The Matrix ◽  
Different Temperatures ◽  
Edx Analyses

The reactivity of CaTi4(PO4)6 (CTP) with alumina and yttria-stabilized zirconia (Y-TZP) ceramics was studied. CTP powder was synthesized and composites with commercial alumina or zirconia matrices containing 10 wt% of CTP were prepared. They were sintered at different temperatures and characterized using XRD, SEM, and EDX analyses. The results showed that the alumina/CTP and Y-TZP/CTP composites start to react below 1000 °C. In the alumina/CTP composite the first reaction product, detected at 970 °C, was AlPO4. At temperatures above 1280 °C TiO2 and CaTiO3 were also formed and no CTP peaks could be detected using XRD analysis. The composite sintered at 1500 °C consisted of Al2O3 matrix, AlPO4, TiO2, CaTiO3 and Al2TiO5. The reaction products formed in the Y-TZP/CTP composite at 970 °C were TiO2 and Ca2Zr7O16. At higher sintering temperatures, 1280 °C and above, CTP was no longer present, Ca2Zr7O16 decomposed, forming CaO2 and ZrO2, and Y2O3 was consumed to form YPO4. Consequently, upon cooling to room temperature the matrix phase transformed to monoclinic ZrO2. Based on these results it can be concluded that CTP is not a suitable bioactive second phase for the fabrication of CTP composites with alumina or zirconia matrices.

“Western” Influence on Some Palace Gardens in Historical Peninsula of Istanbul

2018 ◽  
Vol 43 (4) ◽  
pp. 16-24
Author(s):  
M. Bekar ◽  
M Var
Keyword(s):  
Plant Material ◽  
Industrial Revolution ◽  
Second Step ◽  
Western Influence ◽  
Study Results ◽  
Technological Developments ◽  
Three Stages ◽  
The City ◽  
Over Time ◽  
Main Material

From past to present, Istanbul has witnessed many empires and historical events. This accumulation has made Istanbul one of the most important cities in Turkey. The architecture and historic potential of the city dates back to centuries ago. Palace architecture is the most important cultural inventories of the city. Over time, technological developments and the industrial revolution brought the “western influence” to Turkey. This effect is observed on planning character and on the planting design. The main material of the work is Topkapı Palace, Beylerbeyi Palace and Dolmabahçe Palace. In this context, this paper consist of three stages. Literature studies have been carried out in the first stage. “Western effect” on the palaces has been investigated after the second step consisting of the field study and mapping. As result of the examinations, western influence was studied in three stages as general planning character, structural material and plant material. As a result of the study, results were obtained for each title. Suggestions were made for rehabilitation and palace gardens planning.

A Usability Evaluation of Facebook's Privacy Features Based on the Perspectives of Experts and Users

2019 ◽  
pp. 1544-1568
Author(s):  
Márcio J. Mantau ◽  
Marcos H. Kimura ◽  
Isabela Gasparini ◽  
Carla D. M. Berkenbrock ◽  
Avanilde Kemczinski
Keyword(s):  
Social Networks ◽  
Social Media ◽  
Social Network ◽  
User Interaction ◽  
Usability Evaluation ◽  
Second Step ◽  
Web Based ◽  
The Third ◽  
Privacy Settings ◽  
Three Stages

The issue of privacy in social networks is a hot topic today, because of the growing amount of information shared among users, who are connected to social media every moment and by different devices and displays. This chapter presents a usability evaluation of the privacy features of Facebook's social network. The authors carry out an evaluation composed by three approaches, executed in three stages: first by the analysis and inspection of system's features related to privacy, available for both systems (Web-based systems and mobile-based systems, e.g. app). The second step is a heuristic evaluation led by three experts, and finally, the third step is a questionnaire with 605 users to compare the results between specialists and real users. This chapter aims to present the problems associated with these privacy settings, and it also wants to contribute for improving the user interaction with this social network.

scholarly journals Effect of Sterilization on the Properties of a Bioactive Hybrid Coating Containing Hydroxyapatite

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
E. K. K. Baldin ◽  
C. F. Malfatti ◽  
V. Rodói ◽  
R. N. Brandalise
Keyword(s):  
Electrochemical Behavior ◽  
Morphological Changes ◽  
Xrd Analysis ◽  
Dip Coating ◽  
Open Circuit ◽  
Hybrid Coating ◽  
Mechanical Resistance ◽  
X Ray Diffraction ◽  
Wear Performance ◽  
Different Temperatures

The objective of this study was to evaluate the influence of sterilization on a hybrid coating obtained from a sol composed of alkoxysilane tetraethoxysilane (TEOS) and organoalkoxysilane methyltriethoxysilane (MTES) containing 10% (mass) of hydroxyapatite particles. The coating was obtained by dip coating, by applying two layers (protective/bioactive), which were cured at different temperatures (450°C and 60°C). The effects of sterilization on the superficial, electrochemical, bioactive, and mechanical properties of the coating were evaluated by performing different sterilization processes, namely, steam autoclave, hydrogen peroxide plasma, and ethylene oxide. Subsequently, the coating was characterized by using scanning electron microscopy (SEM/FEG), and FTIR measurements were performed to characterize the chemical structure. The bioactivity and degradability of the coating were analyzed by mass variation after immersion in SBF and X-ray diffraction (XRD) analysis. The electrochemical behavior was assessed by open circuit potential (OCP) and potentiodynamic polarization curves and the mechanical behavior by wear resistance. Results showed that all sterilization processes caused significant morphological changes in the hybrid coating. The autoclaved sample presented the highest structural chemical changes, and, consequently, the highest degradability, even though it had a superior bioactive behavior in relation to the other samples. In addition, the sterilization processes influenced the electrochemical behavior of the hybrid coating and altered the mechanical resistance to abrasion, thus presenting lower wear performance in relation to the nonsterilized sample.

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