scholarly journals Synthesis of SiO2 nanopowders containing quartz and cristobalite phases from silica sands

2015 ◽  
Vol 33 (1) ◽  
pp. 47-55 ◽  
Author(s):  
◽  
Mochamad Zainuri ◽  
◽  

AbstractIn this study, extraction and synthesis of SiO2 nanoparticles from silica sands have been conducted by means of two different methods, i.e. dry method (method 1) and hydrothermal process (method 2). The basic difference between the two methods is in the extraction step. The two methods were compared in terms of being more efficient, economical, and superior in obtaining SiO2 nanoparticles. The SiO2 nanoparticles were characterized in terms of phase purity, crystallinity, Si-O functional bonding as well as particles size and morphology. The most interesting fact in this study was the formation of both quartz and cristobalite phases within all prepared SiO2 nanoparticles.

2007 ◽  
Vol 119 ◽  
pp. 275-278 ◽  
Author(s):  
Upendra A. Joshi ◽  
Jae Sung Lee

The La0.8Sr0.2MnO3 nanocubes have been synthesized by simple precipitation followed by hydrothermal process. The as-obtained nanocubes were characterized by SEM, TEM, EDS, XRD and ICP-AA. The SEM and TEM images clearly showed cube type morphology of reaction product. The XRD pattern gave evidence for the phase purity and high crystallinity of the La0.8Sr0.2MnO3 nanocubes. The ICP-AA analysis along with EDS confirms the stoichiometry of the product. Electrochemical activity for oxygen reduction reaction was carried out in 1 M KOH. The oxygen reduction current measured by cyclic voltametry showed six times higher value for nanocubes than that of bulk catalysts of same composition.


RSC Advances ◽  
2014 ◽  
Vol 4 (78) ◽  
pp. 41578-41583 ◽  
Author(s):  
Tao Yang ◽  
Yangai Liu ◽  
Zhaohui Huang ◽  
Qian Yang ◽  
Yongbo Chen ◽  
...  

Hierarchical peony-like FeCO3 micro-flowers were selectively synthesized via a facile template-free hydrothermal process. Porous α-Fe2O3 derived from FeCO3 maintained the original size and morphology of FeCO3. The excellent lithium storage properties of porous α-Fe2O3 micro-flowers were examined.


2010 ◽  
Vol 4 (3) ◽  
pp. 107-114 ◽  
Author(s):  
Anne Aimable ◽  
Tomasz Strachowski ◽  
Ewelina Wolska ◽  
Witold Lojkowski ◽  
Paul Bowen

This study presents a comparative approach to investigate the potentials of two innovative methods for the synthesis of ZnO and Al-doped ZnO. The first method is a precipitation system working in mild hydrothermal conditions (90?C) using a tubular reactor (Segmented Flow Tubular Reactor, SFTR). The second method is a microwave-assisted hydrothermal process working at 250?C - 38 atmospheres. Nanocrystalline ZnO with a high specific surface area (49-68 m2/g) was obtained with both systems. Smaller equiaxed particles (50-70 nm) were obtained with the SFTR, with an excellent homogeneity in size and morphology, which was attributed to an excellent control of the process parameters (mixing, temperature, volume of reaction). A higher luminescence signal was measured on these samples. The microwave method leads to particles with a higher crystallinity due to the temperature of the reaction. A significant effect of the aluminum was observed, which reduces the crystal growth to produce equiaxed morphologies. This effect was enhanced by adding poly(acrylic) acid (PAA).


1982 ◽  
Author(s):  
Dorothy L. Finley ◽  
H. C. Strasel ◽  
Richard L. Bloom ◽  
John F. Oates

2020 ◽  
Vol 24 (1) ◽  
pp. 100-105
Author(s):  
Herawati Herawati ◽  
Muhammad Arsyad Thaha ◽  
Chairul Paotonan

Abstrak Wilayah pesisir merupakan pertemuan antara wilayah laut dan wilayah darat, dimana daerah ini merupakan daerah interaksi antara ekosistem darat dan ekosistem laut yang sangat dinamis dan saling mempengaruhi. Tujuan penelitian ini adalah untuk menentukan material lokal yang potensial dapat digunakan sebagai bahan bangunan pelindung pantai dan memilih tipe bangunan pelindung pantai yang sesuai kondisi hidro-oseanografi di lokasi studi dengan metode Analythic Hierarchy Process. Lokasi penelitian berada di Provinsi Sulawesi Tenggara, tepatnya di Pulau Kabaena, Kecamatan Kabaena Barat Desa Sikeli kabupaten Bombana. Pulau Kabaena memiliki luas 873 km2. Secara geografis terletak antara 4°22’ 59,4” - 5°28’ 26,7” Lintang Selatan serta antara 121°27’46,7”-122°09’,4” Bujur Timur. Hasil penelitian menunjukkan perairan disepanjang tanjung perak sangat mempengaruhi hidro-oseonografi disekitar pantai desa Sikeli. Kondisi ini berpengaruh terhadap pola pergerakan arus dan tinggi gelombang datang disekitar pantai desa Sikeli. Tinggi gelombang rata-rata yang paling besar merambat dari arah barat sebesar 0.49 m dengan presentase kajadian sebesar 32.42 %, disusul arah barat laut sebesar 0.39 m (20.56 %), arah tenggara sebesar 0.31 m (8.72 %) arah barat daya sebesar 0.31 m (7.99 %), arah utara sebesar 0.20 m (6.94 %), arah timur sebesar 0.15 m (11.81 %), arah selatan sebesar 0.12 m (3.42 %), dan arah timur laut sebesar 0.11 m (8.15 %). Pengambilan keputusan untuk memilih tipe bangunan pelindung pantai dengan metode AHP (Analytical Hierarchy Process) untuk penanganan abrasi pesisir pantai desa Sikeli berbasis bahan lokal diperoleh bahwa alternatif bangunan dengan nilai keterpilihan yang tertinggi adalah detached breakwater (0,4432) disusul groin (0,2479), sea-wall (0,1700) dan revetment (0.1389). Detached breakwater berfungsi untuk menahan laju sedimen kearah laut, mengurangi ketinggian dan meredam energi gelombang dan tidak dibangun sepanjang garis pantai yang akan dilindungi sehingga kapal nelayan dapat ditambat dipesisir pantai dengan aman. Abstract The Selection Type of Coastal Protection Structures in Sikeli Village Based on Local Materials. The coastal area is a meeting point between the sea and land areas, where this area is an area of interaction between terrestrial ecosystems and marine ecosystems which are very dynamic and influence each other. The purpose of this research is to determine local materials that can be used as coastal protection materials and to select the type of coastal protection that is suitable for the hydro-oceanographic conditions in the study location using the Analythic Hierarchy Process method. The research location is in Southeast Sulawesi Province, precisely on Kabaena Island, Kabaena Barat District, Sikeli Village, Bombana Regency. Kabaena Island has an area of 873 km2. Geographically it is located between 4° 22' 59.4"- 5° 28' 26.7" South Latitude and between 121° 27' 46.7 "-122° 09' 4" Longitude East. The results showed that the waters along Tanjung Perak greatly affect the hydro-oseonography around the coast of Sikeli village. This condition affects the current movement pattern and the height of the incoming waves around the coast of Sikeli village. The largest average wave height propagating from the west is 0.49 m with a kajadian percentage of 32.42%, followed by the northwest direction of 0.39 m (20.56%), southeast direction of 0.31 m (8.72%) to the southwest of 0.31 m (7.99%), to the north of 0.20 m (6.94%), to the east of 0.15 m (11.81%), to the south of 0.12 m (3.42%), and to the northeast of 0.11 m (8.15%). The decision to choose the type of coastal protection using the AHP (Analytical Hierarchy Process) method for the coastal abrasion management model in Sikeli village based on local materials was obtained that the alternative building with the highest electability value was the detached breakwater (0.4432) followed by groins (0.2479), sea-wall (0.1700) and revetment (0.1389). The detached breakwater model which functions to restrain the sediment rate towards the sea, reduce the height and reduce wave energy and is not built along the coastline which will be protected so that fishing boats can be moored to the coast safely.


2011 ◽  
Vol 1 (1) ◽  
pp. 36-41
Author(s):  
Jyoti Dhakal

The dentoskeletal characteristics of Class II malocclusion subjects were evaluated using cephalometric radiograph and dental cast of 60 untreated patients. The sample included 30 Class II Division 1 and 30 Class II Division 2 malocclusion patients. The inter-canine, inter-premolar, inter-molar, inter-canine alveolar, inter-premolar alveolar, inter-molar alveolar widths are measured on study models. The result showed statistically significant difference between the groups for mandibular inter-canine width only. The cephalometric analysis revealed that SNB angle was responsible for the skeletal sagittal difference between the two groups except for the position of maxillary incisors. No basic difference in dentoskeletal morphology existed between Class II Division 1 and Class II Division 2 malocclusions.


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