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PREPARATION AND CHARACTERIZATION OF CELLULOSE/HYDROUS NIOBIUM PHOSPHATE HYBRID  [PDF]
Paulo H. Fernandes Pereira,Herman Cornelis Jacobus Voorwald,Maria Odila H. Cioffi,Maria Lucia Caetano Pinto Da Silva
BioResources , 2010,
Abstract: In recent years, increasing attention has been directed to the use of renewable resources, particularly of sugarcane bagasse. Considering the abundant availability of such lignocellulosic materials, relatively few attempts have been made regarding their utilization. Studies about properties and morphology, heavy metal adsorption, and membranes preparation have been conduced by this research group in order to use these materials. In this paper, cellulose fibers obtained from sugarcane bagasse were bleached and modified by hydrous niobium phosphate. Hybrids (cellulose/NbOPO4.nH2O) were prepared from metallic niobium dissolved in a fluoridric/nitric (10:1) mixture, to which cellulose sugarcane bagasse was added. Afterwards a concentrated orthophosphoric acid (85mL, 85% w/w) was added to precipitate hydrous niobium phosphate particles. This material was characterized by X-ray diffraction (XRD), thermogravimetry (TG/DTG), and differential scanning calorimetry (DSC) analyses, as well as scanning electronic microscopy (SEM) coupled to an energy dispersive spectrophotometer (EDS). Morphological studies of bleached cellulose revealed different sizes and arrangement of cells, showing that NbOPO4.nH2O was present in the cellulose structure. Thermal stability of the hybrid was observed up to approximately 200°C, and the cellulose decomposed at 300°C. These data will help finding new uses for these materials.
Preparation and Characterization of Hydrous Zirconium Oxide Formed by Homogeneous Precipitation
Silva, G.L.J.P. da;Silva, M.L.C.P. da;Caetano, Tatiana;
Materials Research , 2002, DOI: 10.1590/S1516-14392002000200011
Abstract: this paper reports on the preparation, characterization and study of the ion exchange behavior of hydrous zirconium oxides formed by homogeneous precipitation from zirconium oxychloride. the precipitants used were obtained by thermal decomposition of urea, sodium nitrite or ammonium carbonate. seven compounds were prepared and characterized by thermal analysis, x-ray diffractometry and by surface area measurements. amorphous forms were obtained in each case, a result that agrees with those obtained by conventional gel precipitation methodology. all these materials present surface area values of >148 m2.g-1, determined after heat treatment at 50 °c. the ion exchange behavior of each hydrous zirconium oxide prepared was studied using k+ as the exchanged species and the results compared with those obtained for hydrous zirconium oxide originally precipitated by the sol gel method.
Preparation and Characterization of Hydrous Zirconium Oxide Formed by Homogeneous Precipitation
Silva G.L.J.P. da,Silva M.L.C.P. da,Caetano Tatiana
Materials Research , 2002,
Abstract: This paper reports on the preparation, characterization and study of the ion exchange behavior of hydrous zirconium oxides formed by homogeneous precipitation from zirconium oxychloride. The precipitants used were obtained by thermal decomposition of urea, sodium nitrite or ammonium carbonate. Seven compounds were prepared and characterized by thermal analysis, X-ray diffractometry and by surface area measurements. Amorphous forms were obtained in each case, a result that agrees with those obtained by conventional gel precipitation methodology. All these materials present surface area values of >148 m2.g-1, determined after heat treatment at 50 °C. The ion exchange behavior of each hydrous zirconium oxide prepared was studied using K+ as the exchanged species and the results compared with those obtained for hydrous zirconium oxide originally precipitated by the sol gel method.
Preparation and Application of Agglomeration-Free and Nanoparticles Zirconia
无团聚纳米氧化锆的制备及应用

JIU Jin-Ting,GE Yue,ZHANG Shu-Rong,LI Li-Ping,TU Fan,ZHU He-Sun,
酒金婷
,葛钥,张涑戎,李立平,屠凡,朱鹤孙

无机材料学报 , 2001,
Abstract: Zirconia with average crystalline size of 20nm, regular spherical particle and agglomeration free was successfully fabricated by surface modification of polymer and heterogeneous azeotropic distillation process. The space obstruct of polymer limits the growth of precursor. The distilla- tion effectively dehydrates hydrous zirconia, which makes butanol molecular substituting water surround the precursor particle. The process prevents the formation of hard agglomerates be- tween zirconia moleculars. When nanoparticles zirconia added, the antifriction properties of 932 lubricating oil can be improved.
A Stabilization Mechanism of Zirconia Based on Oxygen Vacancies Only  [PDF]
Stefano Fabris,Anthony T. Paxton,Michael W. Finnis
Physics , 2002,
Abstract: The microscopic mechanism leading to stabilization of cubic and tetragonal forms of zirconia (ZrO$_2$) is analyzed by means of a self-consistent tight-binding model. Using this model, energies and structures of zirconia containing different vacancy concentrations are calculated, equivalent in concentration to the charge compensating vacancies associated with dissolved yttria (Y$_2$O$_3$) in the tetragonal and cubic phase fields (3.2 and 14.4% mol respectively). The model is shown to predict the large relaxations around an oxygen vacancy, and the clustering of vacancies along the $<111 >$ directions, in good agreement with experiments and first principles calculations. The vacancies alone are shown to explain the stabilization of cubic zirconia, and the mechanism is analyzed.
First-principles molecular-dynamics simulations of a hydrous silica melt: Structural properties and hydrogen diffusion mechanism  [PDF]
Markus Poehlmann,Magali Benoit,Walter Kob
Physics , 2004, DOI: 10.1103/PhysRevB.70.184209
Abstract: We use {\it ab initio} molecular dynamics simulations to study a sample of liquid silica containing 3.84 wt.% H$_2$O.We find that, for temperatures of 3000 K and 3500 K,water is almost exclusively dissolved as hydroxyl groups, the silica network is partially broken and static and dynamical properties of the silica network change considerably upon the addition of water.Water molecules or free O-H groups occur only at the highest temperature but are not stable and disintegrate rapidly.Structural properties of this system are compared to those of pure silica and sodium tetrasilicate melts at equivalent temperatures. These comparisons confirm the picture of a partially broken tetrahedral network in the hydrous liquid and suggest that the structure of the matrix is as much changed by the addition of water than it is by the addition of the same amount (in mole %) of sodium oxide. On larger length scales, correlations are qualitatively similar but seem to be more pronounced in the hydrous silica liquid. Finally, we study the diffusion mechanisms of the hydrogen atoms in the melt. It turns out that HOSi$_2$ triclusters and SiO dangling bonds play a decisive role as intermediate states for the hydrogen diffusion.
Fracture toughness of zirconia ceramic crowns made by feather-edge tooth preparation design  [PDF]
Mirkovi? Nemanja,?padijer-Gostovi? Aleksandra,Lazi? Zoran,Trifkovi? Branka
Vojnosanitetski Pregled , 2012, DOI: 10.2298/vsp100820004m
Abstract: Background/Aim. Fracture toughness determines functional crown strenght and prevents damages on ceramics during mastication. There is a lack of relevant literature data about fracture toughness of crowns made by feather-edge preparation. Mechanical testing of ceramic samples is supposed to show if feather-edge tooth preparation is a successful method for making ceramic crowns without any risk of reduction of their mechanical properties. This research was done to establish effects of feather-edge tooth preparation on fracture toughness of single zirconia ceramic crowns. Methods. The research was performed as an experimental study. Sixty (60) ceramic crowns were made on non-carious extracted human premolars. Thirty (30) crowns were made on the basis of feather-edge preparation (experimental group I). The group II included 30 crowns made on 1 mm rounded shoulder. Crowns fabrication was executed on a copy mill production system “Zirkonzahn” (Zirkonzahn GMBH, Gais, Germany). The spherical compression test was used to determine fracture toughness, using 6 mm diameter ceramic ball. Fracture load for damaging ceramic crown was recorded on a universal testing machine - Zwick, type 1464, with the speed of 0.05 mm/min. Results. The results of this research introduced significant differences between fracture toughness of ceramic samples in every examined group. However, fracture toughness of crowns from both group was above 2 000 N, what was double beyond a recommended value. The mean value of fracture toughness in the feather-edge group was 2 090 N, and in shoulder group it was 2 214 N. Conclusion. This research showed a high fracture toughness of zirconia crowns made on feather-edge preparation. The examined crowns showed a fracture resistance at a sufficient distance in relation to the minimum values of functional loads. Further research of functional loads of these crown is necessary, as well as research of marginal adaptation of cemented crowns and gingival inflammatory response.
Preparation and cytocompatibility of polylactic acid/hydroxyapatite/graphene oxide nanocomposite fibrous membrane
HaiBin Ma,WenXin Su,ZhiXin Tai,DongFei Sun,XingBin Yan,Bin Liu,QunJi Xue
Chinese Science Bulletin , 2012, DOI: 10.1007/s11434-012-5336-3
Abstract: A series of polylactic acid (PLA) based nanocomposite fibrous membranes, including neat PLA, PLA/hydroxyapatite (HA) and PLA/HA/graphene oxide (GO), were fabricated via electrospinning method. The morphology and composition were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) respectively. The thermal stability was determined by thermogravimetric analysis (TGA). To estimate the cytocompatibility of asprepared PLA/HA/GO fibrous membrane, MC3T3-E1 cells were cultured, and the corresponding cell adhesion and differentiation capability were investigated by fluorescence microscopy, SEM and MTT test. The electrospun ternary PLA/HA/GO membrane exhibited three-dimensional fibrous structure with relatively rough surface morphology, which made itself ideal for cell attachment and proliferation in bone tissue regeneration. The fluorescence microscopy, SEM and MTT test confirmed that the PLA/HA/GO nanocomposite fibrous membrane created a proper environment for the seeding and proliferation of MC3T3-E1 cells.
PREPARATION AND PROPERTIES OF FIBROUS MONOLITHIC CERAMICS BY IN SITU SYNTHESISING
原位合成纤维块体陶瓷的制备与性能

GUO Hai,HUANG Yong,
郭海
,黄勇

材料研究学报 , 1997,
Abstract: Preparation of fibrous monolithic ceramics by in situ synthesising is a simple and cheap way to make ceramics with high performance. In this paper, the process of preparing in situ Si3N4 fibrous monolithic ceramics and the main factors which affect properties of the material were investigated. It is found that the reinforcing effect comes from the synergism of the toughening in two different scale. One is the oriented growth of grains or distribution of whiskers in the fibrous cells, the other is the effect of the special fibrous monolithic structure formed by the weak interfaces between fibrous cells. Fibrous monolithic ceramics with high performance have been prepared by in situ synthesising method. The fracture toughness can reach 23.95MPa' m1/2 at room temperature.
Prepare and Formation Mechanism of the Zirconia Coating on Aluminium Alloy by Plasma Electrolytic Oxidation
XIN Shi-Gang,ZHAO Rong-Gen,DU Hui,SONG Li-Xin
无机材料学报 , 2009, DOI: 10.3724/sp.j.1077.2009.00107
Abstract: Zirconia coating was produced on aluminium alloy by plasma electrolytic oxidation (PEO). The alkaline electrolyte containing Zr(OH)a4 powders was used. The composition and structure of the coating were investigated by XRD, EPMA. The results show that the coating consists of a t-ZrO2, a m-ZrO2, a | /SUB>-Al2O3 and a ||/EM>-Al2O3. a t-ZrOa2 is the main phase and distributes in outer layer of the coating, however, a | /EM>-Al2O3 appears in inner layer of the coating. Many micro-particles appear on the coating surface with dimension of a 1£2| aa. In the process of plasma electrolytic oxidation, Zr(OH)a4 powders move and deposite on the mouth of plasma discharge channel under the effect of electric field force, then it is transformed to ZrOa2 by the high temperature of plasma discharge.
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