Well-sinterable Y3Al5O12 Powder from Carbonate Precursor

2000 ◽  
Vol 15 (7) ◽  
pp. 1514-1523 ◽  
Author(s):  
Ji-Guang Li ◽  
Takayasu Ikegami ◽  
Jong-Heun Lee ◽  
Toshiyuki Mori
Keyword(s):  
Precipitation Method ◽  
Yttrium Nitrate ◽  
Mixed Solution ◽  
Formation Temperature ◽  
Constant Heating Rate ◽  
Vacuum Sintering ◽  
Hydrogen Carbonate ◽  
Ammonium Hydrogen ◽  
Constant Heating ◽  
Carbonate Precursor

Carbonate precursors of Y3Al5O12 (YAG) were synthesized from a mixed solution of alum and yttrium nitrate using ammonium hydrogen carbonate as precipitant. Precipitation method (normal-strike or reverse-strike) and aging were found to have dramatic effects on cation homogeneity of the precursor, which in turn influenced the formation temperature of the YAG phase. Reactive YAG powders were produced from the reverse-strike-derived, as-synthesized precursors at temperatures ≤1200 °C. These powders densified to >98.0% of the theoretical density up to 1500 %C at a constant heating rate of 8 %C/min or to transparency by vacuum sintering at 1700 %C for 1 h without additives.

Reactive yttrium aluminate garnet powder via coprecipitation using ammonium hydrogen carbonate as the precipitant

2000 ◽  
Vol 15 (9) ◽  
pp. 1864-1867 ◽  
Author(s):  
Ji Guang Li ◽  
Takayasu Ikegami ◽  
Jong-Heun Lee ◽  
Toshiyuki Mori ◽  
Yoshiyuki Yajima
Keyword(s):  
Theoretical Density ◽  
Mixed Solution ◽  
Vacuum Sintering ◽  
Ammonium Hydrogen Carbonate ◽  
Yttrium Aluminate ◽  
Intermediate Phases ◽  
Hydrogen Carbonate ◽  
Ammonium Hydrogen ◽  
Approximate Composition ◽  
Carbonate Precursor

Ammonium hydrogen carbonate was used as the precipitant to synthesize yttrium aluminate garnet (YAG) precursors from a mixed solution of aluminum and yttrium nitrates via coprecipitation. The carbonate precursor, with an approximate composition of NH4AlY0.6(CO3)1.9(OH)2 · 0.8H2O, transformed to pure YAG at 900 °C without the formation of intermediate phases. Reactive YAG powder was produced by calcining the precursor at 1100 °C. The YAG powder densified to 99.8% of the theoretical density by vacuum sintering at 1500 °C for 2 h, and the sintered body showed transparency. Less agglomeration of the precursor and good dispersity of the resultant YAG powder were responsible for the excellent sinterability.

scholarly journals Fabrication of Dy2O3 Transparent Ceramics by Vacuum Sintering Using Precipitated Powders

2020 ◽  
Vol 7 (1) ◽  
pp. 6
Author(s):  
Dianjun Hu ◽  
Xin Liu ◽  
Ziyu Liu ◽  
Xiaoying Li ◽  
Feng Tian ◽  
...  
Keyword(s):  
Near Infrared ◽  
Optical Quality ◽  
Precipitation Method ◽  
Infrared Range ◽  
Transparent Ceramics ◽  
Vacuum Sintering ◽  
Hydrogen Carbonate ◽  
Ammonium Hydrogen ◽  
Liquid Precipitation ◽  
Near Infrared Range

As a kind of promising material for a Faraday isolator used in the visible and near infrared range, Dy2O3 transparent ceramics were prepared by vacuum sintering from the nano-powders synthesized by the liquid precipitation method using ammonium hydrogen carbonate as precipitant with no sintering aids. The synthesized precursor was calcinated at 950 °C–1150 °C for 4 h in air. The influences of the calcination temperature on the morphologies and phase composition of Dy2O3 powders were characterized. It is found that the Dy2O3 powder calcinated at 1000 °C for 4 h is superior for the fabrication of Dy2O3 ceramics. The Dy2O3 transparent ceramic sample prepared by vacuum sintering at 1850 °C for 10 h, and subsequently with air annealing at 1400 °C for 10 h, from the 1000 °C-calcined Dy2O3 powders, presents the best optical quality. The values of in-line transmittance of the optimal ceramic specimen with the thickness of 1.0 mm are 75.3% at 2000 nm and 67.9% at 633 nm. The Verdet constant of Dy2O3 ceramics was measured to be −325.3 ± 1.9 rad/(T·m) at 633 nm, about 2.4 times larger than that of TGG (Tb3Ga5O12) single crystals.

Process Study on Green Treatment of Waste Anolyte

2014 ◽  
Vol 1015 ◽  
pp. 350-354
Author(s):  
Li Na Chen ◽  
Wan Yi Liu ◽  
Qi Lin Hu
Keyword(s):  
Ph Value ◽  
Removal Rate ◽  
Chemical Precipitation ◽  
Environmental Benefits ◽  
Precipitation Method ◽  
Molar Ratio ◽  
Dihydrogen Phosphate ◽  
Waste Solution ◽  
Hydrogen Carbonate ◽  
Ammonium Hydrogen

Contraposing the waste anolyte of industry, the paper proposed a new chemical precipitation method to recover Mn (II) ions and Mg (II) ions from the waste solution using ammonium hydrogen carbonate and ammonium dihydrogen phosphate as precipitants, respectively. The technological conditions of dealing procedure such as the molar ratio of reactants, pH value, reaction temperature and time, aging time were investigated. The results shown that the removal rate of Mn (II) ions and Mg (II) ions reached to 96 % and 98 %, and the yields of MnCO3 and NH4MgPO4·6H2O reached to 91 % and 94 %, respectively. The residual solution was recycled to realize the treatment greenly, which could meet the needs of production and increase environmental benefits.

Crystal Structure Stabilization of Gadolinium Aluminum Garnet (Gd3Al5O12) and Photoluminescence Properties

2013 ◽  
Vol 544 ◽  
pp. 245-251 ◽  
Author(s):  
Jin Kai Li ◽  
Ji Guang Li ◽  
Xiao Li Wu ◽  
Shao Hong Liu ◽  
Xiao Dong Li ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Thermal Decomposition ◽  
Solid Solutions ◽  
Elevated Temperatures ◽  
Particle Morphology ◽  
Mixed Solution ◽  
Photoluminescence Properties ◽  
Hydrogen Carbonate ◽  
Ammonium Hydrogen ◽  
Structure Stabilization

To suppress the thermal decomposition and to stabilize the crystal structure of Gd3Al5O12 (GdAG) garnet, doping GdAG with smaller Ln3+ (Ln=Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y, respectively) to form (Gd,Ln)AG solid solutions was proposed in work. Carbonate precursors of (Gd,Ln)AG with an approximate composition of (NH4)x(Gd,Ln)3Al5(OH)y(CO3)z•nH2O were synthesized via coprecipitation from a mixed solution of ammonium aluminum sulfate and rare earth nitrate, using ammonium hydrogen carbonate as the precipitant. The precursors and the calcination derived oxides were characterized using FT-IR spectroscopy, DTA/TG, XRD, BET and FE-SEM. The results showed that smaller Ln3+ doping can indeed stabilize GdAG against its thermal decomposition to a mixture of GdAlO3 (GdAP) and Al2O3 phases at elevated temperatures and at the same time effectively lowers the temperature for garnet crystallization. The carbonate precursors are loosely agglomerated and the resultant (Gd,Ln)AG powders show good dispersion and a fairly uniform particle morphology. The (Gd,Ln)AG solid solutions exhibit decreasing lattice parameters along with decreasing radius of the dopant ions at the same dopant content of 50 at%. Photoluminescence properties of some of the garnet solid solutions are also studied. The materials developed herein may potentially be used for photoluminescent and scintillation applications.

Synthesis of AlN Powder from Precipitation Precursor by Carbon Thermal Reduction in Flowing Nitrogen

2012 ◽  
Vol 512-515 ◽  
pp. 24-27 ◽  
Author(s):  
Hui Feng Lu ◽  
Ming Li Qin ◽  
Sui He Jiang ◽  
Ai Min Chu ◽  
Yan Zhang ◽  
...  
Keyword(s):  
Particle Size ◽  
Carbon Black ◽  
Aluminum Nitride ◽  
Reaction Temperature ◽  
Carbon Black Particle ◽  
Precipitation Method ◽  
Ammonium Hydrogen Carbonate ◽  
Ammonium Alum ◽  
Hydrogen Carbonate ◽  
Ammonium Hydrogen

Abstract. Aluminum nitride(AlN) powders were synthesized by carbonthermal reduction of Ammonium aluminum carbonate hydroxide(AACH). The AACH were prepared from ammonium alum and ammonium hydrogen carbonate by precipitation method and AACH adhere to carbon black during precipitation. The precursor has a high reaction activity (near 100% of nitridation ratio after heated in flow nitrogen at 1400°C, 2h). After carbon remove in muffle furnace at 700 °C, white color Aluminum nitride (AlN) powder attained and mean size is 100 nm. The specific surface area of the powders decreased with increasing of concentration of ammonium alum and ammonium hydrogen carbonate, which range from 22 m2/g to 7 m2/g, particle size vary from 58 to 120 nm. Phase presents in the products during heating in flowed nitrogen were observed by X-ray diffraction. The -Al2O3 formed when the precursor heated to 1200°C, AlN was founded at 1300°C and the reaction ended at 1400°C, the reaction temperature and annealing time were much lower than nitridate the mixture of Al2O3 and carbon black. Particle size was increased when reaction temperature increased from 1400°C to 1550°C.

Fabrication of Transparent YAG Ceramics from Co-Precipitation Synthesized Nanopowders

2008 ◽  
Vol 41-42 ◽  
pp. 271-276 ◽  
Author(s):  
Guang Zhe Lv ◽  
Xiao Dong Li ◽  
Di Huo ◽  
Xu Dong Sun ◽  
Shao Wei Chen ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Precipitation Method ◽  
Chemical Compositions ◽  
Vacuum Sintering ◽  
Ammonia Water ◽  
Visible Light Range ◽  
Ammonium Hydrocarbonate ◽  
Co Precipitation ◽  
Carbonate Precursor ◽  
Better Than

YAG nanopowders were synthesized by a co-precipitation method using ammonium hydrocarbonate and ammonia water as the precipitants respectively. The influences of precipitants on chemical compositions, phase transformation and sinterability of the prepared powders, and transmittance of the vacuum-sintered YAG ceramics were studied. The sinterability of powders synthesized using ammonium hydrocarbonate as precipitant is better than that with ammonia water. Pure YAG phase can be obtained by calcining the hydrate precursor at 1200°C, while some impurity phases exist when calcining the carbonate precursor at the same temperature. Transparent YAG ceramics were fabricated by vacuum sintering at 1700°C for 5 h using the YAG nanopowders, and their in-line transmittance is about 60% in the visible light range.

Synthesis and Sintering of Magnesium Aluminate Spinel Nanopowders Prepared by Precipitation Method using Ammonium Hydrogen Carbonate as a Precipitant

2016 ◽  
Vol 690 ◽  
pp. 224-229 ◽  
Author(s):  
Adison Saelee ◽  
Sirithan Jiemsirilers ◽  
Supatra Jinawath ◽  
Karn Serivalsatit
Keyword(s):  
Cost Effective ◽  
Precipitation Method ◽  
Magnesium Aluminate ◽  
Magnesium Aluminate Spinel ◽  
Ammonium Hydrogen Carbonate ◽  
A Value ◽  
Cost Effective Method ◽  
Chemical Inertness ◽  
Hydrogen Carbonate ◽  
Ammonium Hydrogen

Magnesium aluminate spinel (MgAl2O4) is widely used in many engineering applications due to its high melting point (2135°C), high mechanical strength, chemical inertness, and good optical properties. Precipitation method is recognized as a convenient and cost-effective method for the synthesis of nanopowders. In this present work, MgAl2O4 nanopowders were prepared by precipitation method using ammonium hydrogen carbonate as a precipitant. The precipitated precursors were a mixture of ammonium dawsonite (NH4Al (OH)2CO3·H2O) and hydrotalcite (Mg6Al2(CO3)(OH)16·4H2O). After calcining at 1100°C for 2 hours, The MgAl2O4 nanopowders with particle size of 20-170 nm were obtained. The sinterability of the MgAl2O4 nanopowders was evaluated by sintering compacts of the MgAl2O4 nanopowders at temperature of 1300-1650°C for 2 hours. The relative density of the sintered MgAl2O4 ceramics reached about >97% of theoretical density after sintering at 1500°C for 2 hours. The Vicker’s hardness of the sintered ceramics reached a value of 1414 HV (13.9 GPa) after sintering at 1650°C for 2 hours.

Microstructural development of ZnO using a rate-controlled sintering dilatometer

1996 ◽  
Vol 11 (3) ◽  
pp. 671-679 ◽  
Author(s):  
Gaurav Agarwal ◽  
Robert F. Speyer ◽  
Wesley S. Hackenberger
Keyword(s):  
Thermal Expansion ◽  
Heating Rate ◽  
Grain Growth ◽  
Microstructural Development ◽  
Constant Heating Rate ◽  
Temperature Determination ◽  
Grain Sizes ◽  
Rate Controlled ◽  
Temperature Controlled ◽  
Constant Heating

Rate-controlled sintering (RCS) of isostatically pressed particulate compacts of ZnO showed lower average grain sizes and intragranular pore densities than constant heating rate temperature controlled sintering. Valid comparisons of this form could only be made after corrections to hardware and software which reduced specimen creep under dilatometer pushrod load, nonuniform pushrod expansion, reproducible specimen temperature determination, thermal expansion during sintering, and instantaneous termination of sintering at the specified end of RCS. The improved microstructures from RCS were attributed to maximized efficiency of densification, optimizing the time and temperatures permitted for grain growth.

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