scholarly journals Low-temperature precausticizing — a hopeful approach for green liquor desilication

TAPPI Journal ◽  
2017 ◽  
Vol 16 (02) ◽  
pp. 57-61
Author(s):  
Xinxing Xia ◽  
Fang Wang ◽  
Xiaojing Qin ◽  
Tingting Tang ◽  
Tianwen Zhou
Keyword(s):  
Crystal Structure ◽  
Calcium Carbonate ◽  
Low Temperature ◽  
Specific Surface ◽  
Amorphous Material ◽  
Stoichiometric Ratio ◽  
Green Liquor ◽  
Silica Removal ◽  
Rhombohedral Crystal Structure ◽  
Rhombohedral Crystal

We investigated silica removal by low-temperature precausticizing and the properties of second causticizing calcium carbonate (CCC). The results showed that about 89.3% of silica removal was achieved when 20% (the stoichiometric ratio) of causticizing quicklime was added for precausticizing at 20ºC for 60 min. After that, silica removal became slow. When no precausticizing quicklime was used to remove silica, the CCC particles had a rhombohedral crystal structure covered with amorphous material. As precausticizing quicklime was increased to 30%, the amorphous material and the crack disappeared, and the specific surface area decreased significantly. When CCC was used as filler, the Cobb value decreased significantly, and the sizing effect improved as precausticizing quicklime increased.

scholarly journals Analysis Crystal Structure of La0.7Ba(1-xSrx)0.3MnO3 by Sol-Gel Method

2020 ◽  
Vol 3 (1) ◽  
pp. 35-41
Author(s):  
Juli Hartati ◽  
Sitti Ahmiatri Saptari ◽  
Arif Tjahjono
Keyword(s):  
Crystal Structure ◽  
Sol Gel ◽  
Ammonia Solution ◽  
Hot Plate ◽  
Ionic Radii ◽  
Xrd Pattern ◽  
Gel Method ◽  
Sol Gel Method ◽  
Rhombohedral Crystal Structure ◽  
Rhombohedral Crystal

Abstrak.Penelitian tentang struktur kristal  bahan La0.7(Ba1-xSrx)MnO3  menggunakan metode sol-gel telah berhasil dilakukan. Bahan-bahan dasar yang digunakan dicampur di atas hot plate diaduk sambil ditetesi ammonia solution sehingga mencapai pH 7, selanjutnya didiamkan sampai diperoleh bentuk gel. Gel dikeringkan pada suhu 120°C, selanjutnya dilakukan pra-kalsinasi dengan suhu 650°C selama 6 jam, dilanjutkan dengan kalsinasi  pada suhu 1000°C selama 12 jam, dan kemudian disinter pada temperatur 1200°C selama 12 jam. Hasil refinement data  XRD memberikan informasi bahwa struktur kristal  La0.7(Ba1-xSrx)MnO3 adalah rombohedral dengan space grup R-3c. Penambahan substitusi ion Sr2+ mengakibatkan terjadinya penurunan intensitas dan pergeseran puncak ke arah sudut yang lebih besar. Hal ini disebabkan karena pengaruh jari-jari ion Sr2+ yang lebih kecil dibandingkan dengan jari-jari ion Ba2+ . Abstract.In this research,  La0.7(Ba1-xSrx)0.3MnO3  compound (x = 0; 0.2; 0.3; and 0.5) by sol-gel method has been investigated.  The compound used is mixed on a hot plate until reached a pH 7 when dropped ammonia solution, then let stand until turn into a gel. Dehydrated gel at 120°C, pra-calcination at 650°C for 6 hours, calcination t 1000°C for 12 hours, and sintering at 1200°C for 12 hours. The result of refinement XRD pattern shown that samples are single phase with rhombohedral crystal structure with R-3c space group. The intensity decrease and peak list shift to larger angle when Sr-substitution increased, it’s caused  ionic radii of Sr2+ is smaller than Ba2+ .

Influence of Oxide Doping on Co3O4-CeO2 for CO Oxidation

2011 ◽  
Vol 287-290 ◽  
pp. 1718-1722 ◽  
Author(s):  
Jian Xin Cai ◽  
Yi Hao Lv ◽  
Rong Bin Zhang ◽  
Lai Tao Luo
Keyword(s):  
Crystal Structure ◽  
Low Temperature ◽  
Specific Surface ◽  
Co Oxidation ◽  
Surface Area ◽  
Specific Surface Area ◽  
Catalytic Properties ◽  
Co Adsorption ◽  
Adsorption Properties ◽  
Adsorption Performance

Ce0.7M0.3CoOx catalysts were prepared by polyatomic alcohol method. The crystal structure, reduction and adsorption properties, and specific surface were investigated by XRD, TPR, TPD, BET, respectively. The results show that catalysts doped with different oxides can make great effects on the catalytic properties of the Co3O4-CeO2. The interaction between doping oxides (SrO, NiO, La2O3, ZrO2, Nd2O3) and Co3O4-CeO2 is contributed to the change of the reduction and adsorption performance, and specific surface area of the catalysts. SrO doping can promote CeO2 reduction, CO adsorption and low-temperature oxidative activity of the catalysts. The conversion of CO can reach 100% over the Ce0.7Sr0.3CoOx at 120 °C temperature.

Exploring the magneto-volume anomalies in Dy2Fe17 with unconventional rhombohedral crystal structure

2013 ◽  
Vol 61 (20) ◽  
pp. 7931-7937 ◽  
Author(s):  
Pablo Álvarez-Alonso ◽  
Pedro Gorria ◽  
José L. Sánchez Llamazares ◽  
Gabriel J. Cuello ◽  
Inés Puente Orench ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Rhombohedral Crystal Structure ◽  
Rhombohedral Crystal

scholarly journals XAFS study on nanostructured (La;Sr)CoO and (La;Sr)(Co;Fe)O IT-SOFC cathodes

2014 ◽  
Vol 70 (a1) ◽  
pp. C1528-C1528
Author(s):  
Augusto Mejía Gómez ◽  
Joaquín Sacanell ◽  
Analía Soldati ◽  
Marcia Fantini ◽  
Aldo Craievich ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Pore Size ◽  
Reduction Reaction ◽  
Average Pore ◽  
X Ray ◽  
Rhombohedral Crystal Structure ◽  
Sem Study ◽  
Rhombohedral Crystal ◽  
Synchrotron Light ◽  
Mixed Ionic Electronic Conductors

In the last years, extensive research has been devoted to develop novel materials and structures with high electrochemical performance for intermediate-temperatures solid-oxide fuel cells (IT-SOFCs) electrodes. In recent works, we have investigated the structural and electrochemical properties of nanostructured La0.6Sr0.4CoO3(LSCO) and La0.6Sr0.4(Co;Fe)O3(LSCFO) cathodes, finding that they exhibit excellent electrocatalytic properties for the oxygen reduction reaction [1,2]. These materials were prepared by a pore-wetting technique using polycarbonate porous membranes as templates. Two average pore sizes were used: 200 nm and 800 nm. Our scanning electronic microscopy (SEM) study showed that the lower pore size yielded nanorods, while nanotubes were obtained with the bigger pore size. All the samples were calcined at 10000C in order to produce materials with the desired perovskite-type crystal structure. In this work, we analyze the oxidation states of Co and Fe and the local atomic order of LSCO and LSCFO nanotubes and nanowires for various compositions by X-ray absorption spectroscopies. For this purpose we performed XANES and EXAFS studies on both Co and Fe K edges. These measurements were carried out at the D08B-XAFS2 beamline of the Brazilian Synchrotron Light Laboratory (LNLS). XANES spectroscopy showed that Co and Fe only change slightly their oxidation state upon Fe addition. Surprisingly, XANES results indicated that the content of oxygen vacancies is low, even though it is well-known that these materials are mixed ionic-electronic conductors. EXAFS results were consistent with those expected according to the rhombohedral crystal structure determined in previous X-ray powder diffraction investigations.

Crystal structure of intermetallic phase in Fe–20Cr–4Al–0.5Y alloy by convergent beam electron diffraction

1987 ◽  
Vol 2 (1) ◽  
pp. 16-27 ◽  
Author(s):  
Raghavan Ayer ◽  
J. C. Scanlon ◽  
T. A. Ramanarayanan ◽  
R. R. Mueller ◽  
R. Petkovic-Luton ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Hexagonal Phase ◽  
Intermetallic Phase ◽  
Chemical Compositions ◽  
Rhombohedral Crystal Structure ◽  
Rhombohedral Crystal ◽  
Convergent Beam ◽  
Relationship Of ◽  
The Relationship

The crystal structure and chemical composition of the intermetallic phase in a Fe-20%Cr-4%Al-0.5%Y (wt. %) alloy were investigated by electron microscopy. Convergent beam diffraction studies revealed that the intermetallic phase forms in three different crystal structures that could coexist in a single grain of the phase. The dominant crystal structure was shown to be hexagonal (a = 0.85, c = 0.84 nm) with a space group most likely to be P63/mmc. Within the hexagonal phase, regions of a rhombohedral crystal structure (a = 0.85, c = 1.26 nm) were observed that had grown in without an apparent phase boundary separating the two crystal structures. The third crystal structure was determined to be monoclinic (a = 0.97, b = 0.85, c = 1.07 nm, and beta = 97.3°) and formed by twinning on the {10$\overline 1$1} planes of the hexagonal phase. The chemical compositions of regions with different crystal structures were comparable and the stoichiometry of the intermetallic phase corresponds to (Fe,Cr)17 (Al,Y)2. The relationship of the observed crystal structures to those previously reported is discussed.

scholarly journals Microwave Absorbing Properties of Polycrystalline La0.67Sr0.33MnO3

2019 ◽  
Vol 5 (1) ◽  
pp. 22
Author(s):  
Wahyu Dian Laksanawati ◽  
Feli Cianda Adrin Burhendi ◽  
Acep Kusdiwelirawan
Keyword(s):  
Crystal Structure ◽  
Functional Groups ◽  
Reflection Loss ◽  
Single Phase ◽  
Sol Gel ◽  
Gel Method ◽  
Sol Gel Method ◽  
Microwave Absorbing Properties ◽  
Rhombohedral Crystal Structure ◽  
Rhombohedral Crystal

Sample \ce {La_{0.67}Sr_{0.33}MnO3} has been successfully synthesized by sol gel method shown by the results of XRD formed a single phase with rhombohedral crystal structure. The results of SEM showed particles are agglomerated yet functional groups \ce {Mn-O-Mn} has been formed based on the results of FTIR. The ability of the sample to absorb the microwaves still lower that the value of reflection loss obtained at $-26.05$ dB.

The solubility of calcium carbonate  in green liquor handling systems

TAPPI Journal ◽  
2019 ◽  
Vol 18 (10) ◽  
pp. 595-602
Author(s):  
ALISHA GIGLIO ◽  
VLADIMIROS G. PAPANGELAKIS ◽  
HONGHI TRAN
Keyword(s):  
Calcium Carbonate ◽  
Systematic Study ◽  
Kraft Pulp ◽  
Thermodynamic Simulation ◽  
Solubility Data ◽  
Pulp Mills ◽  
Persistent Problem ◽  
Green Liquor ◽  
Kraft Pulp Mills ◽  
Salt Systems

The formation of hard calcite (CaCO3) scale in green liquor handling systems is a persistent problem in many kraft pulp mills. CaCO3 precipitates when its concentration in the green liquor exceeds its solubility. While the solubility of CaCO3 in water is well known, it is not so in the highly alkaline green liquor environment. A systematic study was conducted to determine the solubility of CaCO3 in green liquor as a function of temperature, total titratable alkali (TTA), causticity, and sulfidity. The results show that the solubility increases with increased temperature, increased TTA, decreased causticity, and decreased sulfidity. The new solubility data was incorporated into OLI (a thermodynamic simulation program for aqueous salt systems) to generate a series of CaCO3 solubility curves for various green liquor conditions. The results help explain how calcite scale forms in green liquor handling systems.

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