排序方式: 共有10条查询结果,搜索用时 15 毫秒
1
1.
Mihalache Valentina Mercioniu Ionel Aldica Gheorghe Pasuk Iuliana 《Journal of Thermal Analysis and Calorimetry》2018,132(1):463-469
Journal of Thermal Analysis and Calorimetry - Azobenzenes undergo reversible trans–cis photo-isomerization and have been studied extensively as photo-responsive materials. Despite their... 相似文献
2.
Marin Cernea Gianluca Poli Gheorghe Virgil Aldica Ciceron Berbecaru Bogdan Stefan Vasile Carmen Galassi 《Current Applied Physics》2012,12(4):1100-1105
(Bi0.5Na0.5)TiO3 was doped in situ with 5, 8, and 11 mol% BaTiO3 (BNT-BTx; x = 0.05, 0.08 and 0.11) using a sol-gel technique. The resulting powders from gel precursors showed microstructures consisting of nano-sized grains and crystalline perovskite structure. Spark plasma sintering (SPS) technique was used to prepare high densified (98–99%ρtheor) BNT-BTx ceramics from these nanopowders. The results confirm the spark plasma sintering method applied to nano-scale powders, obtained by sol-gel, as a viable route in producing nanostructured ceramics. The evolution of the structure and electrical properties of the ceramics with BaTiO3 concentration (x) was investigated. The permittivity of BNT-BT0.08 ceramic is higher (εr = 2090, at 100 kHz) than that for x = 0.05 (εr = 1350) and x = 0.11 (εr = 1800). BNT-BT0.08 ceramic shows maximum values for the frequency constants (Np, Nt), piezoelectric charge coefficient (d31) and piezoelectric voltage coefficient (g31), and minimum values for the electromechanical coupling factor (kp) and piezoelectric charge coefficient (d33). The electrical properties of these ceramics are influenced by grains size, oxygen deficiency and non-uniform internal stresses due to these oxygen deficiencies. BNT-BTx ceramics sintered by SPS seem to be good ceramic resonators with high mechanical quality factor (Qm). 相似文献
3.
Amorphous Bi4Ge3O12 glass samples were produced by melt quenching procedure stating with Bi4Ge3O12 (BGO) powder, obtained by solid state reaction between oxides. The kinetics of non-isothermal crystallization of BGO nano-crystals has been investigated. Differential Thermal Analysis (DTA) can give the main parameters of crystallization with an exothermic peak from 813 K to 851 K depending on the heating rate, which was assigned to the crystallization of cubic BGO in the amorphous matrix and compared with the X-Ray Diffraction (XRD) patterns. The nano-crystal dimensions were calculated from the XRD patterns by using the Debye–Scherrer method and were compared with Transmission Electron Microscopy (TEM) images. It was shown that the Ozawa model is most suitable for describing the behavior of non-isothermal crystallization of BGO nano-crystals within the glass matrix. Experimental results suggest a disk-shape type growth mechanism for the Bi4Ge3O12 nano-crystallites. The Flynn–Wall–Ozawa method has shown that the average activated energy value is 385 ± 14 kJ/mol which was computed within the same model and agrees very well with the activation energy of the crystallization. 相似文献
4.
Santanu Kumar Padhi Nicoletta Baglieri Valentina Bonino Angelo Agostino Lorenza Operti Nicolae Dan Batalu Mariana Carmen Chifiriuc Marcela Popa Mihail Burdusel Mihai Alexandru Grigoroscuta Gheorghe Virgil Aldica Dana Radu Petre Badica Marco Truccato 《Molecules (Basel, Switzerland)》2021,26(16)
We report for the first time on the antimicrobial activity of MgB2 powders produced via the Reactive Liquid Infiltration (RLI) process. Samples with MgB2 wt.% ranging from 2% to 99% were obtained and characterized, observing different levels of grain aggregation and of impurity phases. Their antimicrobial activity was tested against Staphylococcus aureus ATCC BAA 1026, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, and Candida albicans ATCC 10231. A general correlation is observed between the antibacterial activity and the MgB2 wt.%, but the sample microstructure also appears to be very important. RLI-MgB2 powders show better performances compared to commercial powders against microbial strains in the planktonic form, and their activity against biofilms is also very similar. 相似文献
5.
6.
Petre Badica Nicolae Dan Batalu Mariana Carmen Chifiriuc Mihail Burdusel Mihai Alexandru Grigoroscuta Gheorghe Virgil Aldica Iuliana Pasuk Andrei Kuncser Marcela Popa Angelo Agostino Lorenza Operti Santanu Kumar Padhi Valentina Bonino Marco Truccato 《Molecules (Basel, Switzerland)》2021,26(19)
Pristine high-density bulk disks of MgB2 with added hexagonal BN (10 wt.%) were prepared using spark plasma sintering. The BN-added samples are machinable by chipping them into desired geometries. Complex shapes of different sizes can also be obtained by the 3D printing of polylactic acid filaments embedded with MgB2 powder particles (10 wt.%). Our present work aims to assess antimicrobial activity quantified as viable cells (CFU/mL) vs. time of sintered and 3D-printed materials. In vitro antimicrobial tests were performed against the bacterial strains Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 25923, Enterococcus faecium DSM 13590, and Enterococcus faecalis ATCC 29212; and the yeast strain Candida parapsilosis ATCC 22019. The antimicrobial effects were found to depend on the tested samples and microbes, with E. faecium being the most resistant and E. coli the most susceptible. 相似文献
7.
8.
Gheorghe Aldica Carmen Matei Adelina Paun Dan Batalu Marilena Ferbinteanu Petre Badica 《Journal of Thermal Analysis and Calorimetry》2017,127(1):173-179
Additives to MgB2 can improve the superconducting functional characteristics, such as critical current density (J c) and irreversibility field (H irr). Recently, we have shown that repagermanium (C6H10Ge2O7) is an effective additive, enhancing both J c and H irr. To look into details of the processes taking place during the reactive sintering, a thermal analysis study (0.167 K s?1, in Ar) is reported. We used differential scanning calorimetry between 298 and 863 K and simultaneous thermogravimetric—differential thermal analysis between 298 and 1233 K. Samples were mixtures of powders with composition 97 mol% MgB2 and 3 mol% C6H10Ge2O7. Up to 863 K, repagermanium decomposes by multiple steps and forms amorphous phases. A reaction with MgB2 is not observed. Above this temperature, partial decomposition of MgB2 occurs. Crystalline Ge and MgO are detected before formation of Mg2Ge and MgB4, when temperature approaches the melting point of Ge (1211 K). Carbon substitution for boron in the crystal lattice of MgB2 is observed for samples heated above 863 K. The amount of substitutional C does not significantly change with temperature. 相似文献
9.
Transparent oxyfluoride glass-ceramic in the system SiO2–Al2O3–CaF2–EuF2 containing Eu-doped CaF2 nanocrystals were produced by using the controlled crystallization of melt-quenched glass. X-ray diffraction and transmission electron microscopy data have revealed the formation of the CaF2 nanocrystals of about 65 nm size. Photoluminescence spectra have shown an increase of the splitting of the luminescences associated to the Eu3+ ion along with annealing time which is consistent with the Eu3+ environment evolving from a glassy to a crystalline state. 相似文献
10.
D. Barb L. Diamandescu D. Tarină G. Aldica E. Cruceanu 《Hyperfine Interactions》1990,55(1-4):1183-1186
Mössbauer measurements were performed on polycrystalline57Fe: Bi2Sr2Ca1Cu2O y , super-conductor in the temperature range of 77–296 K. The samples were obtained in a solid phase synthesis using 0.01, 0.03, 0.1 and 0.5 mol fractions of α-Fe2O3 (96% enriched in57Fe). A prevailing quadrupole doublet practically independent of temperature and iron concentration characterizes the obtained Mössbauer spectra. The corresponding hyperfine parameters suggest the presence of high spin Fe111 ions in a strongly distorted octahedral symmetry which indicates a probable copper substitution by iron in the system. 相似文献
1