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1.
Glass of composition 40SiO2–20B2O3–30CaO–10M2O3 (M = Al, Cr, Y and La) were prepared by the splat quenching technique to investigate the effect of M2O3 on their bioactivity, structural and optical properties. Y2O3 and Cr2O3 containing glasses formed a crystalline hydroxyapatite (HA) layer after dipping in simulating body fluid (SBF) for 25 days. On the other hand, HA layer could not form in Al2O3 and La2O3 glasses. However, during soaking in SBF solution, these glasses exhibit higher dissolution rate, lower density and increased optical band gap as compared to unsoaked glasses. Their oxygen molar volume was also higher than for Y2O3 and Cr2O3 glasses. The change in composition affects the cross-link formation in the glass matrix and finally its durability and bioactivity in SBF. The results show that M2O3 plays an important role in controlling chemical durability and bioactivity of the glasses.  相似文献   

2.
3.
《Ceramics International》2022,48(13):18730-18738
A series of new negative temperature coefficient (NTC) thermal materials based on (Ba0.85Ca0.15)1-xCex/2(Zr0.1Ti0.9)O3 (0.00 ≤ x ≤ 0.20) ceramics were synthesized by a solid-state method. X-ray diffraction, scanning electron microscope and X-ray photoelectron spectroscopy were used to demonstrate the crystal structure, morphology, and composition of the (Ba0.85Ca0.15)1-xCex/2(Zr0.1Ti0.9)O3 ceramics, which were composed of solid solution based on the BaTiO3 phase. The average grain size of doped ceramic samples experienced the process of first decreasing and then increasing. The doping of Ce has reduced the sintering temperature. The temperature-dependent resistance analysis revealed that with the change of doping amount x, the thermal constant B300/1200 (1.21 × 104–1.13 × 104 K) and the activation energy Ea300/1200 (0.9777–1.0471eV) was initially increased to maximum values at x = 0.05, followed by the decreasing when x > 0.05. It has been established that the concentration of oxygen vacancies is affected by the transition between Ce4+ and Ce3+ provided by high levels of Ce doping. (Ba0.85Ca0.15)1-xCex/2(Zr0.1Ti0.9)O3 ceramics exhibited excellent negative temperature characteristics in the range of 300–1200 °C. Moreover, the temperature resistance linearity was improved after samples were aged. Hence, the (Ba0.85Ca0.15)1-xCex/2(Zr0.1Ti0.9)O3 ceramics were regarded as a promising material for high-temperature NTC thermistors in a wide temperature range.  相似文献   

4.
《Ceramics International》2016,42(10):11858-11865
Glass and in-situ nanocrystalline glass-ceramics of compositions 45SiO2-25CaO-10Na2O-5P2O5-xFe2O3-(15-x) MnO2 are investigated for their magnetic and in-vitro bioactive properties. The ferrimagnetic character is observed in the high Fe2O3 containing in-situ nanocrystalline glass-ceramics. Saturation magnetization and coercivity increases with Fe2O3. After soaking in the simulated body fluid (SBF), the powdered as well as the bulk glasses and glass-ceramics are investigated using various characterization techniques. The presence of MnO2 increases the leaching of Na+ ions from the glasses and also attracts the Ca2+ cations from the SBF as compared to Fe2O3 containing nano-crystalline glass-ceramics. It also increases the tendency to form hydroxyl apatite (HAp) layer. Microwave Plasma Atomic Emission Spectroscopy (MP-AES), Fourier Transform Infrared (FTIR) spectra, X-ray diffraction and Scanning electron micrographs (SEM) after soaking in the SBF confirm the HAp formation on the surface of all the glasses and glass-ceramics. Urbach energy also indicates the structural modifications on the surfaces of the glass and glass-ceramics after soaking in the SBF.  相似文献   

5.
《Ceramics International》2023,49(20):33051-33056
Transverse vibrations of bridging atoms in framework structure oxides contribute to negative thermal expansion (NTE), increasing the configurational entropy. Herein, the configurational entropy of NTE (Al1/3Fe1/3Cr1/3)2Mo3O12 (AFCM) is tuned by introducing ZrMg and W to AlFeCr and Mo sites to lower NTE. The NTE of ((Zr1/2Mg1/2)x(Al1/3Fe1/3Cr1/3)(1-x))2Mo3O12 (ZMAFCM) reduce obviously with increasing the content of ZrMg and also the phase transition temperatures (PTTs) (x = 0∼0.5). For ((Zr1/2Mg1/2)x(Al1/3Fe1/3Cr1/3)(1-x))2(Mo1/2W1/2)3O12 (ZMAFCMW), the NTE and PTTs reduce at a faster rate than that of ZMAFM. The configurational entropy increases with the content of ZrMg firstly (x = 0∼0.4) and then decreases. The possible mechanism of thermal expansion change is related to the enhanced lattice configuration, high entropy. The inconsistent transverse vibrations of bridging oxygen atoms could reduce their contribution to NTE, especially for high entropy. The PTT of high configurational entropy oxides is reduced obviously due to the influenced on the effective electronegativity. The investigation paves a high entropy way to lower thermal expansion and PTT of A2M3O12 oxide ceramics and explores the further mechanism of NTE.  相似文献   

6.
《Ceramics International》2022,48(15):21187-21193
To obtain comprehensive materials with both high temperature coefficient of resistivity (TCR) and magnetoresistance (MR) at low magnetic fields, polycrystalline La0.72Ca0.28Mn1?xCrxO3 (x = 0, 0.02, 0.04, 0.06) ceramics were prepared herein by sol–gel method. Electronic configuration of Cr3+ ions is similar to that of Mn4+ ions, therefore, successive substitution of Mn with Cr increases electrical resistivity and decreases metal–insulator transition temperature of ceramics, even yielding hump-like feature for Cr-rich (x = 0.06) samples. The best TCR (28.50%·K?1) and MR (72.37%) values were obtained simultaneously at Cr dopant content of 0.02 (La0.72Ca0.28Mn0.98Cr0.02O3). Strong response of the material to temperature and magnetic field was caused by minimal symmetry of orthorhombic structure and the most robust Jahn–Teller distortion. With increasing Cr content, Mn3+/Mn4+ or Mn3+/Cr3+ double exchange was diluted, and Cr3+/Cr3+ or Cr3+/Mn4+ superexchange was promoted. However, the internal competition effect was not conducive to the improvement of material properties.  相似文献   

7.
《Ceramics International》2020,46(15):24071-24082
Pristine chromium oxide (Cr2O3) and nickel ions (Ni2+) substituted Cr2O3 nanoparticles were synthesized using a simple co-precipitation technique. The main objective of this work is to investigate Ni2+ substituent's role at different concentrations on the structural, morphological, optical, and magnetic properties of Cr2O3 nanoparticles. Structural analyses based on X-ray diffraction (XRD), Raman and Fourier transform infra-red (FTIR) data confirmed the successful incorporation of Ni2+ into Cr2O3 nanoparticles up to x = 0.05 of Ni2+ content, without affecting the rhombohedral crystal structure of Cr2O3 nanoparticles. Rietveld refinement results showed the variation in lattice parameters and cell volumes alongwith the substitution of Ni2+ into Cr2O3 nanoparticles. Raman and FTIR spectra also depicted a considerable shift in the characteristic vibration modes of Cr2O3 nanoparticles due to strain-induced by Ni2+ substitution. Beyond x = 0.05, the structural transformation took place from rhombohedral to cubic crystal structure. Subsequently, new peaks (apart from Cr2O3 phase modes) have been observed at x = 0.1 of Ni2+ content due to the formation of secondary phase i.e., nickel chromate (NiCr2O4). Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) illustrated the changes in the morphology of Cr2O3 nanoparticles with Ni2+ substitution. UV–Vis analysis revealed a narrowing of optical band energy (Eg) of Ni2+ substituted Cr2O3 nanoparticles from 3 to 1.85 eV as Ni2+ content varies from x = 0 to 0.2, respectively. Afterward, there is an increase in optical band gap energy (Eg) when Ni2+ content increased from x = 0.3 to 0.5, as NiCr2O4 started dominating the Cr2O3 phase. Single-phase Ni2+ substituted Cr2O3 nanoparticles exhibited a superparamagnetic behavior, whereas the multi-phase compound ascribed to both superparamagnetic and paramagnetic. These changes in optical and magnetic properties can lead to novel strategies to render applications in the field of optoelectronics and optomagnetic devices.  相似文献   

8.
Silicon-substituted hydroxyapatite (Si-HA) with up to 1.8 wt% Si content was prepared successfully by a hydrothermal method, using Ca(NO3)2, (NH4)3PO4 or (NH4)2HPO4 and Si(OCH2CH3)4 (TEOS) as starting materials. Silicon has been incorporated in hydroxyapatite (HA) lattice by partially replacing phosphate (PO43−) groups with silicate (SiO44−) groups resulting in Si-HA described as Ca10(PO4)6−x(SiO4)x(OH)2−x. X-ray diffraction (XRD), Fourier transform IR spectroscopy (FTIR), inductively coupled plasma AES (ICP-AES) and scanning electron microscopy (SEM) techniques reveal that the substitution of phosphate groups by silicate groups causes some OH loss to maintain the charge balance and changes the lattice parameters of HA. The crystal shape of Si-HA has not altered compared to silicon-free reference hydroxyapatite but Si-incorporation reduces the size of Si-HA crystallites. Based on in vitro tests, soaking the specimens in simulated body fluid (SBF), and MTT assays by human osteoblast-like cells, Si-substituted hydroxyapatite is more bioactive than pure hydroxyapatite.  相似文献   

9.
《Ceramics International》2016,42(10):11687-11691
In this paper, a series of novel luminescent Sr10−x(SiO4)3(SO4)3O:xEu2+ phosphors with apatite structure were synthesized by a high temperature solid-state reaction. The phase structure, photoluminescence (PL) properties, as well as the PL thermal stability were investigated. Sr9.92(SiO4)3(SO4)3O:0.08Eu2+ phosphor exhibits better thermal quenching resistance, retaining the luminance of 66.55% at 150 °C compared with that at 25 °C. The quenching concentration of Eu2+ in Sr10(SiO4)3(SO4)3O was about 0.08 (mol) with the dipole–quadrupole interaction. The Sr10−x(SiO4)3(SO4)3O:xEu2+ phosphors exhibited a broad-band green emission at 538 nm upon excitation at 396 nm. The results indicate that Sr10−x(SiO4)3(SO4)3O:xEu2+ phosphors have potential applications as near UV-convertible phosphors for white-light UV LEDs.  相似文献   

10.
《Ceramics International》2022,48(24):36358-36370
Ca3(Ti1-xCox)2O7 ceramics were prepared by a tartaric acid sol-gel method and sintered in an oxygen atmosphere. The introduction of Co2+/Co3+ as acceptor dopants leads to the formation of more oxygen vacancies and defect dipoles in Ca3(Ti1-xCox)2O7 ceramics. Oxygen vacancy and defect dipoles lead to the transition of dielectric, leakage, and ferroelectric behaviors of Ca3(Ti1-xCox)2O7 ceramics. The coexistence of hybrid improper ferroelectricity and ferromagnetism at room temperature in Ca3(Ti1-xCox)2O7 ceramics has been successfully realized through the superexchange interaction of Co–O–Co. Ca3(Ti1-xCox)2O7 ceramics exhibit superior ferroelectricity (the remnant polarization is 3.29 μC/cm2) and enhanced ferromagnetism (the remnant magnetization reaches 6.4×10?3 emu/g). This strategy based on the introduction of transition metal ions with unfilled 3d shells at B sites is an important approach to realize novel room-temperature single-phase multiferroic materials for Ca3Ti2O7-based materials.  相似文献   

11.
《Ceramics International》2016,42(5):5842-5857
The effect of SrO substitution for CaO in two sol–gel glasses with different chemical compositions (mol%) A2Sr: (54−x)CaO–xSrO–6P2O5–40SiO2 and S2Sr: (16−x)CaO–xSrO–4P2O5–80SiO2 (x=0, 1, 3 and 5) stabilized at 700 °C on their structure (XRD, FTIR) and bioactive properties (SBF test) was investigated. Preliminary in vitro tests using human articular chondrocytes of selected A2Sr glass were also conducted. Moreover, the subject of this study was to detect the changes on material properties after heat treatment at 1300 °C. The results show that the effect of strontium substitution on structure, bioactivity and crystallization after treatment at both the above temperatures strongly depends on CaO/SiO2 molar ratio. The presence of 3–5 mol% of strontium ions creates more expanded glass structure but does not markedly affect crystallization ability after low temperature treatment. Sintering at 1300 °C of A2 type glasses results in crystallization of pseudowollastonite, hydroxyapatite and also Sr-substituted hydroxyapatite for 3–5 mol% of SrO substitution. The increase of strontium concentration in silica-rich materials after sintering leads to appearance of calcium strontium phosphate instead of calcium phosphate. Bioactivity evaluation indicates that substitution of Sr for Ca delays calcium phosphate formation on the materials surface only in the case of silica-rich glasses treated at 700 °C. Calcium-rich glasses, after both temperature treatments, reveals high bioactivity, while crystal size of hydroxyapatite decreases with increasing Sr content. High temperature treatment of high-silica glasses inhibits their bioactivity. Preliminary in vitro tests shows Sr addition to have a positive effects on human articular chondrocytes proliferation and to inhibit cell matrix biomineralization.  相似文献   

12.
The predominant phase of calcium sulfoaluminate cement, Ca4(Al6O12)SO4, was investigated using high‐pressure synchrotron X‐ray diffraction from ambient pressure to 4.75 GPa. A critical review of the crystal structure of Ca4(Al6O12)SO4 is presented. Rietveld refinements showed the orthorhombic crystal structure to best match the observed peak intensities and positions for pure Ca4(Al6O12)SO4. The compressibility of Ca4(Al6O12)SO4 was studied using cubic, orthorhombic, and tetragonal crystal structures due to the lack of consensus on the actual space group, and all three models provided similar results of 69(6) GPa. With its divalent cage ions, the bulk modulus of Ca4(Al6O12)SO4 is higher than other sodalites with monovalent cage ions, such as Na8(AlSiO4)6Cl2 or Na8(AlSiO4)6(OH)2·H2O. Likewise, comparing this study to previous ones shows the lattice compressibility of aluminate sodalites decreases with increasing size of the caged ions. Ca4(Al6O12)SO4 is more compressible than other cement clinker phases such as tricalcium aluminate and less compressible than hydrated cement phases such as ettringite and hemicarboaluminate.  相似文献   

13.
《Ceramics International》2022,48(8):11056-11063
Ce2[Zr1?x(Ca1/3Sb2/3)x]3(MoO4)9 (CZ1?x(CS)xM) (x = 0.02–0.10) ceramics were prepared by the conventional solid-state reaction method. The correlations between the chemical bond parameters and microwave dielectric properties were calculated and analyzed by using the Phillips–Van Vechten–Levine (P–V–L) theory. Phase composition and microstructures were evaluated by scanning electron microscopy and X-ray diffraction patterns. Lattice parameters were obtained by Rietveld refinements based on XRD data. Excellent properties for Ce2[Zr0.96(Ca1/3Sb2/3)0.04]3(MoO4)9 ceramic sintered at 775 °C: εr = 10.68, Q×f = 85,336 GHz and τf = ?7.58 ppm/°C were achieved.  相似文献   

14.
Solid solutions Ca(DxM1?x)O3 (M = Ti, Zr and D = Fe,Cr), have been studied as ceramic pigment in conventional ceramic glazes using 0.5 mol/mol of NH4Cl as flux agent by solid state reaction and by ammonia coprecipitation route. Ca(CrxTi1?x)O3 compositions obtained without addition of NH4Cl as mineralizer, produce pink color in glazes at low x but CaCrO4 crystallizes when x increases, producing undesired green colors. The crystallization of chromates can be avoided using NH4Cl as mineralizer, giving a complete solid solution that produce pink color in glazes at low x and dark blue shades at high x. Coprecipitated sample produce blue colors at low x and at low temperature than ceramic sample (1000 °C instead 1200 °C for CE sample). Cr4+ ion acts as red chromophore, but at higher x values (blue samples) Cr3+ ion entrance affects the color. Ca(FexTi1?x)O3 system crystallizes perovskite CaTiO3 and pseudobrookite Fe2TiO5 together with rutile as residual crystalline phase, glazed samples change from a yellow to a pink color associated to the increase of pseudobrookite with firing temperature. Ca(FexTi1?x)O3 and Ca(CrxZr1?x)O3 systems crystallize perovskite CaZrO3 and zirconia (ZrO2) in both monoclinic and cubic polymorphs, but iron or chromium oxides are not detected in the powders. Coprecipitated sample stabilises cubic form. The solid solution is not reached completely in these samples and is not stable in glazes.  相似文献   

15.
Surfactant‐assisted hydrothermal synthesis of magnesium‐doped hydroxyapatite (Ca10?xMgx(PO4)6(OH)2) with 0 ≤ x ≤ 1) was realized in aqueous solution at 90°C. β‐TCP phase was formed in the Mg0.6‐HA sample after heat treatment at 1000°C. Magnesium was found to degrade the sintering ability of Mgx‐HA ceramics. Flexural strength (σf) was found to decrease as a function of Mg‐doped HA. The using of carbon nanotubes as reinforcing agents mitigated the strength loss of Mg‐HA ceramics. The flexural strength of Mg0.6‐HA was then increased by nearly 20% from approximately 33 to 39 MPa with an optimum addition of 3 wt% of multi‐walled nanotubes.  相似文献   

16.
《Ceramics International》2023,49(13):21308-21323
Cu-doped solid solutions Ca10.5–xCux(PO4)7 with β-Ca3(PO4)2 (β-TCP) structure were synthesized using high-temperature solid-state synthesis. Correctly characterizing the location of Cu2+ in the structure is important for a correct understanding of the biological properties formation. The limit of Ca10.5–xCux(PO4)7 solid solutions without impurity phases was found at x = 1.5. The crystal-chemical analysis reveals that the Cu2+ ions cannot be located in the M4 site of the β-TCP-type structure due to the very distorted environment. The Cu2+ ions preferably occupy the M5 site (x ≤ 1.00) and then located in the M3 and M2 sites (x > 1.00). The chemical composition, local environment, and structural features of Ca10.5–xCux(PO4)7 phosphates were investigated by a complex of methods. The antibacterial properties were studied on one fungus (C. albicans) and four bacteria (E. coli, E. faecalis S. aureus and P. aeruginosa). Biocompatibility tests were performed on human bone marrow mesenchymal stem cells (hMSCs). The biological response of the Cu2+ strongly depends on the occupied ion position and its concentration. The concentration-dependent behavior of the bacteria growth inhibition was observed, and the sample with x = 1.33 exhibits the highest activity between single-phase samples. Further increasing of bacteria growth inhibition is attributed to Ca3Cu3(PO4)4 impurity phase. Also, antimicrobial properties depend on the Cu2+ location in the β-TCP crystal structure in accordance with ion release behavior. The Cu2+ location in the large M3 polyhedra leads to a noticeable increase in ion release. Biocompatibility assays on hMSCs showed the absence of cytotoxicity in direct and indirect contact for single-phase samples. In the biphasic sample the presence of impurity Ca3Cu3(PO4)4 phosphate at 2 wt% causes a cytotoxicity effect. Thus, phase purity plays a critical role in understanding the regularities of bioactive properties formation. This work can be an initial basis for further investigations of the site-selective arrangement of bioactive ions, such as Cu2+ and other similar ions, in the β-TCP structure to enhance biological potential.  相似文献   

17.
Chromium borides of various phases were fabricated through combustion synthesis in the mode of self-propagating high-temperature synthesis (SHS) by adopting the powder compacts of Cr2O3 + xB (with x = 4–9) and Cr2O3 + 2Al + yB (with y = 1–8). Because aluminothermic reduction of Cr2O3 is more exothermic than borothermic reduction, the reaction temperature and combustion front velocity of the Al-added samples are much higher than those of the Cr2O3–B samples. In agreement with the composition dependence of reaction exothermicity, the fastest combustion wave was observed in the compact with x = 6 for the Cr2O3–B sample and y = 4 for the Cr2O3–Al–B sample. According to the XRD analysis, Cr5B3, CrB, and CrB2 were produced in the monolithic form respectively from the Cr2O3–B samples of x = 4, 5, and 9, or in the composite form from samples of other stoichiometries. On the other hand, five different borides were identified in Al2O3-added products. Among them, Cr2B, CrB, and CrB2 were yielded as the sole boride compound from the Al-added samples of y = 1.2, 3, and 7 or 8, respectively. Cr5B3 and Cr3B4 were produced along with CrB as the secondary phase. Based upon experimental evidence, it was found that an excess amount of boron in the reactant mixture was required to facilitate the formation of chromium borides.  相似文献   

18.
The (1 ? y)La1?xSmx(Mg0.5Sn0.5)O3yCa0.8Sm0.4/3TiO3 ceramics were prepared by the conventional solid-state method. The X-ray diffraction patterns of the La1?xSmx(Mg0.5Sn0.5)O3 ceramics revealed that La1?xSmx(Mg0.5Sn0.5)O3 is the main crystalline phase, which is accompanied by a little La2Sn2O7 as the second phase. An apparent density of 6.59 g/cm3, a dielectric constant (?r) of 19.9, a quality factor (Q × f) of 70,200 GHz, and a temperature coefficient of resonant frequency (τf) of ?77 ppm/°C were obtained when the La0.97Sm0.03(Mg0.5Sn0.5)O3 ceramics were sintered at 1500 °C for 4 h. The temperature coefficient of resonant frequency (τf) increased from ?77 to +6 ppm/°C as y increased from 0 to 0.6 when the (1 ? y)La0.97Sm0.03(Mg0.5Sn0.5)O3yCa0.8Sm0.4/3TiO3 ceramics were sintered at 1500 °C for 4 h. 0.425La0.97Sm0.03(Mg0.5Sn0.5)O3–0.575Ca0.8Sm0.4/3TiO3 ceramic that was sintered at 1500 °C for 4 h had a τf of ?3 ppm/ °C.  相似文献   

19.
We report on the individual roles of charge carrier density and network modification in sodium ion conducting glasses from the Na2O-P2O5-SO3-AlF3 (NAPFS) system. For this, a broad range of glass compositions was considered across the series of 44Na2O/(56 – x − y)P2O5/xAlF3/ySO3, 47Na2O/(53 − x − y)P2O5/xAlF3/ySO3, and 50Na2O/(50 − x − y)P2O5/xAlF3/ySO3, with x = 8, 12, 16, 20 and y = 0, 5, 7, 10, 12. Impedance spectroscopy was conducted on these glasses at frequencies from 10−2 to 106 Hz and over temperatures from 50 to 250°C, and complemented by structural analyses using Raman spectroscopy and nuclear magnetic resonance data. While the trends in dc conductivity and activation energy follow that of Na2O content (increasing from 44 to 50 mol%), substantial enhancement of conductivity (by about two orders of magnitude) and correspondingly lower activation energy were also found for constant Na2O concentration when adjusting SO3 or AlF3 within specific limits of glass structure.  相似文献   

20.
Cr-doped Li3V2−xCrx(PO4)3/C (x = 0, 0.05, 0.1, 0.2, 0.5, 1) compounds have been prepared using sol–gel method. The Rietveld refinement results indicate that single-phase Li3V2−xCrx(PO4)3/C with monoclinic structure can be obtained. Although the initial specific capacity decreased with Cr content at a lower current rate, both cycle performance and rate capability have excited improvement with moderate Cr-doping content in Li3V2−xCrx(PO4)3/C. Li3V1.9Cr0.1(PO4)3/C compound presents an initial capacity of 171.4 mAh g−1 and 78.6% capacity retention after 100 cycles at 0.2C rate. At 4C rate, the Li3V1.9Cr0.1(PO4)3/C can give an initial capacity of 130.2 mAh g−1 and 10.8% capacity loss after 100 cycles where the Li3V2(PO4)3/C presents the initial capacity of 127.4 mAh g−1 and capacity loss of 14.9%. Enhanced rate and cyclic capability may be attributed to the optimizing particle size, carbon coating quality, and structural stability during the proper amount of Cr-doping (x = 0.1) in V sites.  相似文献   

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