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1.
We report a study on the effect of the substitution of Bi3+ by Sr2+ on the stabilization of R3c structure of Bi1?xSrxFeO3 (0 ≤ x ≤ 0.3, Δx = 0.05), and its effect in the magnetic and dielectric behavior. Stoichiometric mixtures of Bi2O3, Fe2O3 and SrO were mixed and milled for 5?h using a ball to powder weight ratio of 10:1 by high-energy ball milling. The obtained powder were pressed at 900?MPa to obtain cylindrical pellets and sintered at 800?°C for 2?h. X-ray diffraction and Rietveld refinement were used to evaluate the effect of Sr2+ on the crystal structure. In addition, vibrating sample magnetometry (VSM) and dielectric tests were used for describing the multiferroic behavior. The results show that Sr-doped BiFeO3 particles present rhombohedral structure (R3c) characteristic of α-BiFeO3 when the doping is below 0.10?mol of Sr. Additionally, a gradual decrease in the amount of secondary phases with the increase of the amount of strontium is observed. For doping concentration higher than 0.15?mol of Sr, a phase transition to an orthorhombic symmetry (β-BiFeO3, Pbnm) is detected. Besides, changes in relative intensities of reflection peaks planes (110) and (104) are associated with the phase transformations and with the magnetic and dielectric behavior. The α-BiFeO3 phase show antiferromagnetic behavior and high values of dielectric permittivity, whereas the β-BiFeO3 phase show a ferromagnetic behavior and low dielectric permittivity.  相似文献   

2.
Structural and mechanical Characterizations of La1.8M0.2NiO4+δ (M: Sr and Ba) prepared by low frequency ultra-sound assisted synthesis technique and sintered at different temperatures were studied. HRTEM and XRD analyses showed the uniform shape of calcined nanocrystalline powders with the particle size of less than 100?nm with mixed phases, which were refined by Rietveld method using orthorhombic (Fmmm) and tetragonal (F4/mmm) structures. Sintering La1.8Sr0.2NiO4+δ and La1.8Ba0.2NiO4+δ compacted discs at temperatures higher than 1300?°C and 1250?°C, respectively, resulted in appearance of extra peaks close to a monoclinic phase. Doping La2NiO4+δ with Sr2+ and Ba2+ did not affect its sinterability and average grain size significantly, however, Ba2+ improved the elastic modulus and microhardness, while Sr2+ improved the fracture toughness.  相似文献   

3.
β-tricalcium phosphate (β-TCP) is an ideal biomaterial for the bone repair because of its biocompatibility and biodegradability. In this study, 0 mol%, 5 mol%, 15 mol% and 30%mol bivalent manganese ion (Mn2+) doped β-TCP (Mn-TCP) powders were synthesized by a sol-gel method. The amount of the dopants significantly influences the crystallinity and the parameters related with structure of β-TCP, such as the lattice parameters and crystallite dimensions. The particle size and the particle distribution of doped β-TCP powers were evaluated as well. Meanwhile, the as-synthesized powders were consolidated by sintering at 1000 °C in muffle furnace for 5 h to get Mn-TCP porous material and the degradation experiment was carried out in Simulated Body Fluid (SBF) solution for 28 days. Then, Mn-TCP porous material were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscope (SEM). Significantly, there were bone-like apatite materials deposited on the surface of bone-like porous materials. With the increasing doping amount of Mn2+, the newly formed apatite-like materials decreased, while the crystallinity increased significantly. Besides, pH results showed that alkaline environment was more favorable for the formation of sedimentary materials.  相似文献   

4.
In the present work, a new composite between β-tricalcium phosphate (a bioceramic material) and barium zirconium titanate (a ferroelectric material) were fabricated. Beta-tricalcium phosphate (β-TCP) powder was synthesized from egg shells while barium zirconium titanate powder was synthesized from metal oxide powders. The composites were fabricated by a solid-state reaction method. Effects of barium zirconium titanate on many properties of the composites were investigated. Barium zirconium titanate additive improves the electrical properties of the composites such as dielectric, ferroelectric and piezoelectric properties. Furthermore, the mechanical properties, such as hardness are improved by the additive. In-vitro bioactivity test suggests that β-tricalcium phosphate has a higher apatite forming ability as compared to the BZT. The obtained results indicate that the composites are a promising biomaterial candidate.  相似文献   

5.
CaTi1-x (Mg1/2W1/2)xO3 (x = 0, 0.02, 0.04, 0.06, 0.08) dielectric ceramics were synthesized via the traditional solid-state reaction method. Crystal structure and microwave dielectric properties of CaTi1-x (Mg1/2W1/2)xO3 system were systematically investigated based on chemistry bond theory (P–V-L theory) for the first time. The pure perovskite phase was obtained for all doped samples, as confirmed through the XRD and Rietveld refinement results. The lattice characteristics were closely related to the microwave dielectric properties. The bond ionicity, lattice energy, and bond energy affected the dielectric constant, quality factor, and temperature stability of the ceramic material. Through the use of (Mg1/2W1/2)4+ doped on B-site, the CaTi1-x (Mg1/2W1/2)xO3 system can maintain a high dielectric constant (εr > 100) while effectively reducing the τf value from 800 ppm/°C to less than 300 ppm/°C and improving the Q × f value to 9650 GHz (at 3.76 GHz).  相似文献   

6.
The crystal structure, electronic structure, and optical properties of Eu-doped γ-AlON at various Eu concentrations were obtained from density functional theory. Based on the calculated results, the luminescence properties and mechanism of Eu-doped γ-AlON are discussed. The calculated results demonstrate that AlON:Eu2+ phosphor exhibits a direct band gap, which is advantageous for luminescence. The absorption spectrum of AlON:Eu2+ phosphor has a single intense broad absorption band from 275 to 425 nm with a peak at 355 nm, which is consistent with corresponding experimental excitation spectra. The existence of Eu?N bonds enhanced the local covalence of Eu2+, hence the optical stability of AlON:Eu2+ phosphor.  相似文献   

7.
《Ceramics International》2021,47(18):25514-25519
Y3+- and Co2+-substituted Sr1-xYxFe12-xCoxO19 (0 ≤ x ≤ 0.50) M-type hexaferrites were synthesized using a traditional oxide ceramic process to study their structural and static magnetic properties. The well-defined M-type phase structures of the pure and Y–Co co-substituted strontium ferrites were verified via XRD analysis. When the Y–Co substitution amount (x) exceeded 0.20, the Fe2O3, Y3Fe5O12, SrFe2O4, and CoFe2O4 impurity phases coexisted in the M-type strontium hexaferrite structure. The lattice parameters a and c increased when x ≤ 0.20; however, a further increase in the Y–Co substitution caused them to decrease. The X-ray density dx initially decreased when x ≤ 0.20, and subsequently increased with a further increase in Y–Co substitution. The density of the sintered samples ds exhibited a decreasing trend with the increasing Y–Co substitution, inducing the porosity to increase. The saturation magnetization Ms monotonously decreased with the increasing Y–Co substitution amount. The in-plane and out-of-plane coercivities, Hc(ip) and Hc(op), initially increased as x increased from 0 to 0.20. When x > 0.20, however, Hc(ip) exhibited a decreasing trend; particularly, a linear decrease was observed as x increased from 0.30 to 0.50. The squareness ratio S reached its maximum (79.6%) at x = 0.20.  相似文献   

8.
The effect of the sintering conditions (temperature and time) on the microstructure (density and grain size) and mechanical properties (hardness, elastic modulus, and strength) of β-tricalcium phosphate (β-TCP) bioceramics fabricated from Ca-deficient commercial powders is analyzed. Contrary to current general opinion, it is demonstrated that the optimal sintering temperature to maximize the mechanical performance of this β-TCP material is not necessarily below the β ? α transformation temperature (1125 °C). In particular, optimal performance was achieved in samples sintered at 1200 °C for 3 h, since it was not until higher temperatures or longer sintering times that microcracking develops and mechanical properties are degraded. It is argued that the residual stresses developed during this reversible transformation do not lead to microcrack propagation until sufficiently large starting flaws develop in the microstructure as a consequence of grain growth. Implications of these findings for the processing routes to improve sintering of this important bioceramic are discussed.  相似文献   

9.
Microwave assisted synthesis method is a relatively new approach employed to decrease synthesis time and form a more homogenous structure in biphasic calcium phosphate bioceramics. In this study, nanocrystalline HA/β-TCP composites were prepared by microwave assisted synthesis method and, for comparison reason, by conventional wet chemical methods. The chemical and phase composition, morphology and particle size of powders were characterized by FTIR, XRD and SEM, respectively. The use of microwave irradiation resulted in improved crystallinity. The amount of hydroxyapatite phase in BCP ranged from 5% to 17%. The assessment of bioactivity was done by soaking of powder compacts in simulated body fluid (SBF). The decreasing pH of the solution in the presence of β-TCP indicated its biodegradable behavior. Rod-like hydroxyapatite particles were newly formed during the treatment in SBF for microwave assisted substrate synthesis. In contrast, globular particles precipitate under same conditions if BCP substrates were synthesized using conventional wet chemical methods.  相似文献   

10.
针对四川盆地地下卤水富含钾锶的特点,采用等温溶解平衡法研究308K下四元体系Na+,K+,Sr2+//Br-–H2O的相平衡关系,测定平衡液相的溶解度,通过实验数据绘制该四元体系308 K下的平衡相图和水图,同时对该四元体系Na+,K+,Sr2+//Br-–H2O在不同温度下的溶解度数据进行比较分析和讨论。结果表明在308K下该四元体系是一个简单的共饱和类型,且既无复盐也无固溶体形成,该相图包含一个共饱点,3条单变量曲线和3个固相结晶区,分别对应为KBr、NaBr·2H2O和SrBr2·6H2O,其中KBr结晶区最大,而NaBr·2H2O和SrBr2·6H2O的结晶区较小。通过对比多温相图发现,NaBr和SrBr2的溶...  相似文献   

11.
This paper reports on the results of the investigation of aluminum potassium barium phosphate glasses that contain copper and iron additives and have compositions similar to the composition of the matrix of the KGSS 0180/35 neodymium phosphate glass used for fabricating large-sized active elements intended for high-power laser amplifiers with a high output energy. The redox equilibrium of iron ions has been studied as a function of the melting temperature of the glass (850, 1100, and 1300°C). The redox equilibrium of iron or copper ions and their contributions to the nonactive absorption coefficient of glasses prepared at the melting temperature (1100°C) or after cooling of the glass melt at different rates to the glass making temperature (850°C) have been investigated. It has been established that a decrease in the melting temperature of the glass leads to a shift in the redox equilibrium of iron ions toward the formation of Fe3+ ions. During cooling of the glass melt from 1100 to 850°C, the redox equilibrium of copper (iron) ions shifts toward the formation of Cu2+ (Fe3+) ions; in this case, the lower the rate of cooling the melt, the larger the shift. At the minimum rate of cooling the glass melt (250°C for 180 min), the contribution of copper ions to the nonactive absorption coefficient increases by 25%, whereas the corresponding contribution of iron ions decreases by 40%.  相似文献   

12.
《Ceramics International》2017,43(11):8348-8355
Ceramic-metal composite materials, namely cermets, are provided with characteristics of both ceramic and metal. Herein, for the first time bio-cermets based on β-tricalcium phosphate (β-TCP) bioceramic with biodegradable iron being reinforcement phase, were fabricated using the powder metallurgic method. The phase composition, microstructure, mechanical properties and in vitro cell behaviors of bio-cermets were investigated. The results revealed that atomic diffusion occurred between the iron and β-TCP matrix during the sintering process. The bio-cermets attained remarkable increase in fracture toughness (1.16–1.55 MPa m1/2) compared to the β-TCP bioceramic (0.54 MPa m1/2). The bio-cermets with 10 vol% iron showed the highest compressive strength (640 MPa), significantly higher than that of plain β-TCP bioceramic (285 MPa). The in vitro cell behaviors test indicated that the bio-cermets did not showed any sign of toxicity; the iron ions released from bio-cermets up-regulated bone-related gene expression of bone mesenchymal stem cells. The bio-cermets developed in this study represent potential bone substitutes for application in the load-bearing bone defects.  相似文献   

13.
通过控制变量法考察温度、浓度对焙烧镁铝类水滑石得到的层状双金属氧化物(LDO)吸附Cd2+、Cu2+、Zn2+单一离子及其共存体系的影响。结果表明,LDO对单一离子吸附效果均较好,温度升高,有利于LDO吸附Cd2+、Cu2+、Zn2+;Cu2+-Cd2+、Cd2+-Zn2+共存时,LDO吸附效果为Cu2+> Cd2+、Zn2+> Cd2+;三者共存时,LDO吸附效果为Cu2+> Zn2+> Cd2+。  相似文献   

14.
以稻草秸秆为原料,用多种胺基试剂经氯化和胺化反应对稻草秸秆进行改性,制成多种改性胺基稻草纤维并用于电镀废水中重金属离子Fe3+、Ni2+、Cu2+、Zn2+的吸附,并用扫描电子显微镜、X射线衍射仪等分析手段对改性纤维的表面形貌和结构性能进行了表征。实验结果表明:乙二胺基稻草纤维吸附Fe3+、Ni2+、Cu2+、Zn2+性能明显优于稻草纤维原料和其他胺基改性稻草纤维;胺基改性稻草纤维对金属离子吸附能力与含氮量有一定相关性;乙二胺基稻草纤维吸附电镀废液中Fe、Ni、Cu、Zn效果明显。  相似文献   

15.
Bi2O3·2B2O3 glasses doped with La2O3 and Er2O3 were prepared by the melting-quenching method with AR-grade oxides. IR analysis was used to investigate the glass network structure. The characteristic temperatures including the glass transition temperature (Tg), crystallization temperature (Tp), and melting temperature (Tm) were estimated by DSC. The coefficient of thermal expansion (α), mass density (D), and Vickers hardness (Hv) were also measured. The results show that the basic network structure of Bi2O3·2B2O3 glasses doped with rare-earth oxides consists of chains composed of [BO3], [BO4], and [BiO6] units. La2O3 and Er2O3 act as network modifiers. As the doping concentrations of the rare-earth oxides were increased, Tg increased and α decreased, indicating that a more rigid glass was obtained. Er2O3 reduces the melting temperature and prevents glass crystallization. La2O3 contributes to the improvement of the microhardness of Bi2O3·2B2O3 glass.  相似文献   

16.
BaAl2?2xNi2xSi2O8?x (x = 0, 0.005, 0.01, 0.02, 0.03) ceramics were prepared using traditional solid phase reaction method. The microwave dielectric properties, including permittivity (εr), quality factor (Q × f), and temperature coefficient of resonant frequency (τf), were discussed based on the bond valence theory. The first-principle calculation was adopted to determine the site (Ba, Al, and Si) where doping element (Ni2+) would be inclined to occupy. The substitution of Ni2+ for Al3+ contributed to the breaking of Al-O and Si-O bonds and then facilitated the BaAl2Si2O8 (BAS) hexacelsian-celsian transformation. Moreover, this substitution could change the bond strength between cation and oxygen anion due to the variation of the bond valence, which reasonably explained the variation of εr, Q × f, and τf values. Well-sintered and completely transformed celsian ceramics can be obtained after doping with Ni2+. When x = 0.01, compact BaAl1.98Ni0.02Si2O7.99 ceramic exhibited highly promising microwave dielectric properties: εr = 6.89, Q × f = 53, 287 GHz and τf = -25.31 × 10?6 /°C.  相似文献   

17.
Sr1−xCaxFe12−xGdxO19 (x = 0, 0.04, 0.08, 0.12, 0.16, 0.20) hexaferrites were characterized by several techniques, such as X-ray diffraction, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy, and vibrating sample magnetometer. Structural results indicate the formation of a pure-phase Sr1−xCaxFe12−xGdxO19 hexaferrite with space group P63/mmc. SEM photography confirms that there are a smaller number of defects due to the reduced porosity and surface area (increased particle size). Magnetic investigations showed a rise of the coercive force from 5069.8 to 5757.4 Oe and saturation magnetization from 79.25 to 80.68 emu/g. The maximum values appear to be for sample x = 0.16, which may be useful in such as permanent magnets, and high-density media for magnetic storage devices. Dielectric parameters, such as conductivity, the real part of permittivity, dielectric loss, dielectric tangent loss, and complex modulus, were studied. Impedance analysis shows that the conduction process is mainly governed by the long-range movement of the charge carriers based on the Debye model for x = 0.12.  相似文献   

18.
以改性火山岩颗粒作为吸附材料,处理含Cu2+和Zn2+重金属废水,探讨了pH、温度、改性火山岩投加量、吸附时间对吸附性能的影响。结果表明,当pH在3~6之间时,随着pH的增大,改性火山岩颗粒对Cu2+和Zn2+去除率显著提高,当pH大于6后,改性火山岩颗粒对Cu2+和Zn2+去除率增速变缓,并伴有沉淀出现;温度的影响表明:随温度升高改性火山岩颗粒对Cu2+和Zn2+去除效率升高,分析认为该过程是吸热反应,且为自发过程;对Cu2+吸附去除,改性火山岩颗粒最佳投加为10 g/L,对Zn2+吸附去除,改性火山岩最佳投加量为6 g/L;改性火山岩颗粒对Cu2+和Zn2+吸附去除过程属于快吸附过程,饱和吸附时间为8 h。  相似文献   

19.
通过研究Ce3+、Nb5+、Zn2+对钛酸锶钡基陶瓷介电性能的影响,结果发现Ce3+、Nb5+、Zn2+各离子单一掺杂提高其介电性能是有限的,而充分运用各微量离子作用机理,控制钛酸锶钡的Ce3+、Nb5+、Zn2+引入量,能综合提高钛酸锶钡基陶瓷的介电性能。  相似文献   

20.
分别采用荧光光谱(FS)、紫外可见吸收光谱(UV-Vis)以及圆二色谱(CD)考察了2种金属离子Cu2+、Zn2+对牛血清白蛋白(BSA)-盐酸小檗碱(BC)结合过程的变构效应,得到表征BSA内源荧光猝灭、BSA-BC复合物稳定性、BC在BSA分子上的结合位点数发生变构的定量变构系数βQ、βA、βn。结果表明,Cu2+/Zn2+对BC猝灭BSA内源荧光呈正变构效应(βQ>1),且变构效应随Cu2+/Zn2+浓度的增大呈现一定的饱和性;而对BSA-BC复合物稳定性以及BC在BSA分子上的结合位点数呈负变构效应(0<βA<1,0<βn<1),且变构效应随Cu2+/Zn2+浓度的增大呈现不同变化趋势;BSA分子构象转变可能是产生变构效应的主要原因。  相似文献   

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