Synthesis and characterization of nm-sized PbTiO3 crystallites

In this work attempt is made to synthesize PbTiO₃(PT) nanopowder by low temperature direct synthesis (LTDS) method already introduced by Wada et al. [8]. Various samples were prepared by precipitating a strong acidic Ti-bearing solution in an alkaline solution obtained by dissolution of Pb(NO₃)₂ in a KOH solution (pH = 14). The samples were synthesized with varying Pb/Ti atomic ratios (1.0, 2.7, 6.5 and 10) at 70 ^∘C. XRD, TEM, FTIR and DTA/TG techniques were utilized to characterize the obtained powders. The formation of single phase PT was not confirmed for the non-heat treated as precipitated samples in contrast with the results obtained by Wada et al. [8] for BaTiO₃. Further, for the as precipitated samples not subjected to washing process with a Pb/Ti ratio above 1, the formation of unknown crystalline phase/s was detected due to the reaction taken place between Ti-bearing solution and potassium plumbate formed by dissolution of Pb(NO₃)₂ in KOH solution. Applying washing process for these samples gave rise to the partial destruction of the observed structure/s and the formation of an amorphous phase as confirmed by XRD and TEM results. However, calcination of the as precipitated/washed samples at 500 ^∘C and 700 ^∘C for 1 hour gave rise to the formation of PT nanopowder as the main phase with average crystallite sizes in the range of about 11–14.5 nm respectively. Single phase PT nanopowder of an average crystallite size of 13 nm was formed for the sample with a Pb/Ti ratio = 1 when calcined at 500 ^∘C for 1 hour. For the calcined samples with Pb/Ti ratios above 1 the formation of PbO as the second phase, however, was also detected and its level of formation was found to be related to the Pb/Ti ratio.     

Synthesis and characterization of thermoplastic polyurethane/montmorillonite nanocomposites produced by reactive extrusion

The novel polyurethane/montmorillonite (PU/MMT) nanocomposites based on poly (propylene oxide) glycol (POP), 4,4′-diphenymethylate diisocyanate (MDI), 1,4-butanediol (1,4-BD) and MMT has been synthesized using a one-step direct polymerization-intercalation technique by twin-screw extruder. Its structure and thermal properties are characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM) and High-resolution electron microscopy (HREM), Fourier-transform infrared spectroscopy (FTIR) and Thermogravimetry analysis (TGA), respectively. The results of XRD and HREM analyses show that the silicate layer is well dispersed in PU matrix and this mesostructure can be considered as a delaminated nanocomposites. The TGA analysis indicates that the thermal stability properties of the PU/MMT nanocomposites are increased slightly compared with the pristine PU, due to the increase of the char residue. The mechanical and flammability performances are examined by electronic Universal Tester and Cone calorimetry, respectively. The layered silicate, which acts as a high aspect ratio reinforcement, enhances tensile strength of the PU. Specifically, there is a 25% increase in the tensile strength of PU nanocomposites containing 4 wt.% MMT compared with that of pristine PU. However, the elongation at break of PU/MMT nanocomposites is lower than that of pristine PU. The loading of MMT leads to the remarkably decrease of heat release rate (HRR), contributing to the improvement of flammability performance.     

Preparation of PbTiO3 fibres using triethanolamine-complexed alkoxide

Abstracts are not published in this journal     

PbTiO3纳米晶的制备及表征

以硬脂酸、乙酸铅和钛酸丁酯为原料用硬脂酸凝胶法合成ＰｂＴｉＯ３纳米晶原粉，利用改进的烧结设备，同时采用Ｎ２气氛下预烧，通过调节Ｎ２和Ｏ２的流量控制烧结气氛，得到粒径重复性好的ＰｂＴｉＯ３纳米晶，用差热分析，热重分析和Ｘ－射线衍射对合成过程进行了研究，用透射电镜考查纳米晶的粒度和形貌，用５ＤＸ－红外光谱仪对ＰｂＴｉＯ３纳米晶的红外透射谱进行了测试分析。     

Synthesis and electrical studies of modified PbTiO3 ceramics: (Pb1−x Ca x ) (Mn0·05W0·05Ti0·90) O3

Modified ceramics (Pb_1−x Ca _x )[(Mn_0·5W_0·5)_0·10Ti_0·90]O₃ have been fabricated forx=0, 0·05, 0·10 and 0·15 by high temperature solid state reaction technique. XRD, SEM, DTA and electrical studies of the sample withx=0·10 have been performed. These studies show that the sample is homogeneous single phase perovskite type with tetragonal structure. The phase transition occurs at 330°C. Electrical behaviour of other samples have also been investigated as a function of frequency (1 kHz to 1 MHz) and temperature (26°C to 300°C). The samples withx=0·05 and 0·10 have low loss, low dielectric constant, and show negligible pyroelectric effect. The sample withx=0·15 has minimum values ofɛ and loss which are temperature independent up to about 200°C. It also shows good pyroelectric behaviour. Hence it may be of use in pyroelectric infrared sensors.     

纳米晶钛酸铅的合成及其介电性能的研究

采用硬脂酸凝胶法(SAG)制各了纳米晶PbTiO3，用差热—热重分析、红外光谱分析、X光衍射分析及透射电镜等手段对产物的形成过程、晶型、粒径进行了表征。通过对材料介电性能的研究发现，纳米晶钛酸铅在接近静态条件下的低频介电常数远大于常规材料的介电常数，随着粒径的减小，纳米晶钛酸铅的低频介电常数逐渐增大。     

纳米Fe3O4修饰槲皮素-锗配合物的合成与表征

为制备具有磁性靶向作用的杭癌药物,采用槲皮素经乙醇溶解后加入锗标准溶液,水浴搅拌回流后抽滤、洗涤、干燥,得到槲皮素-锗的配合物,再加入分散在乙醇中的纳米Fe3O4 30℃反应24h可得到具有顺磁性的槲皮素-锗的金属配合物,对其进行紫外、红外光谱测定及磁强度测试.结果表明,槲皮素的A环和C环形成锗配合物的可能性较大,槲皮...     

On the structural and electrical properties of modified PbTiO3 ceramics

Ceramics (Pb_0·75Ca_0·25)[(Ni_1/2W_1/2) _y Ti_1−y ]O₃ fory = 0 ·05, 0·10, 0·15 and 0·30 have been prepared using high temperature solid state reaction method. X-ray analyses show that these materials are of single-phase perovskite type tetragonal structure. To solve inaccuracy in finding para-ferroelectric phase transition temperatureT _c(ε _max), we have carried out the analyses of the data using a computer program. The role of Ni and W as modifiers on structural and electrical (dielectric and pyroelectric) properties is discussed in terms of the usefulness of these materials. Results indicate that ceramic Pb_0·75Ca_0·25Ni_0·25W_0·025Ti_0·95O₃ is a good candidate for pyroelectric applications. Paper presented at the poster session of MRSI AGM VI, Kharagpur, 1995     

Synthesis of PbTiO3 film on LaNiO3-coated substrate by the spray-ICP technique

In an attempt to utilize LaNiO₃ as a bottom electrode for PbTiO₃ ferroelectric film, PbTiO₃ and LaNiO₃ films were prepared by the spray-ICP technique under atmospheric pressure. The dense LaNiO₃ films crystallized with preferred (1 1 1) and (1 0 0) orientations on sapphire (0 0 1) and MgO (1 0 0), respectively. Resistivities of the LaNiO₃ films deposited above 600 °C were about 4 × 10^–6 m. The PbTiO₃ film with preferred (001) orientation was successfully prepared on LaNiO₃-coated MgO (1 0 0). Its dielectric constant and dissipation factor were about 200 and 0.02, respectively, at 1 kHz. The Curie temperature suggested that PbTiO₃ films were free from contamination by LaNiO₃.     

Characterization of modified PbTiO3 ceramic particles by statistical treatment of their size distribution

Microstructural characteristics of (Pb, Ca)TiO₃ piezoelectric ceramic particles have been deduced from computer analysis of their images and the corresponding statistical treatment of the data obtained. It is intended that this study should be used as a nexus, or link, between the geometrical parameters of these particles and some of their physical properties.     

Poly-L-lactic acid braided fibres produced by melt spinning: characterization and in vitro degradation

Bioabsorbable fibres showing stress at break of 500 MPa and modulus of 10 GPa, have been obtained through a melt-spinning, hot-drawing process. Multifilament braids present the characteristic S-shaped stress-strain curve of human ligaments. Mechanical behaviour is affected by twisting and braiding such that stiffness can vary from 0.8 GPa to 6.2 GPa, covering the whole ligament physiologic range, reported to be 1.5 GPa, according to age and sport activity. A cyclic tension load applied for 2×10⁶ cycles lead to initial mechanical improvement and causes no creep. During degradation in vitro, yield stress increases continuously while the ultimate tensile strength (UTS) starts to decrease after 5 weeks. After 13 weeks degradation, strength loss amounts to 6% of the initial UTS. At this time the surface of the fibres shows isolated longitudinal cracks.This paper was accepted for publication after the 1995 Conference of the European Society of Biomaterials, Oporto, Portugal, 10–13 September     

有机硅改性聚氨酯微球的合成及性能研究

以甲苯二异氰酸酯(TDI)、聚己内酯二元醇(PCL)、端羟基聚二甲基硅氧烷(DHPDMS)和二羟甲基丙酸(DMPA)为主要原料,通过自乳化的方法合成DHPDMS改性聚氨酯微球。考察了n(NCO)/n(OH)、DHPDMS的质量分数、DHPDMS的分子量、乳化时间和CaCl2浓度对改性聚氨酯溶液外观、黏度(η)、溶胀率(Sw)以及微球的形态和硬度等性能的影响。并通过FTIR和SEM表征微球的化学结构和表面形态结构。FTIR表明硅氧键引入到聚氨酯中;SEM照片显示改性聚氨酯微球为表面多孔隙球形,直径为2 mm左右,内有空腔,空腔直径为1 mm左右。结果表明,DHPDMS质量分数为8%、分子量为4500时改性聚氨酯微球的耐水性和力学性能都有明显的提高。     

Synthesis and characterization of silver-carbon nanoparticles produced by high-current pulsed arc

In this paper, we report the formation of silver-carbon encapsulated metal nanoparticles (EMN's) using a high-current pulsed arc system in an argon atmosphere. The deposits were studied by Optical Extinction Spectroscopy (OES), X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM); the chemical analysis of the deposits was performed using Energy Dispersion X-ray spectroscopy (EDX). Using the total nanoparticle diameter, the bulk crystalline density of silver and an estimate amorphous carbon (a-C) density we have calculated the size of the silver nucleus and the thickness of the a-C coating as a function of the argon gas pressure. The OES spectra of the EMN's exhibited two peaks characteristic of the Surface Plasmon Resonance (SPR) of elongated/very close silver nanoparticles; a subsequent thermal annealing strongly increased the SPR peaks. The double peak SPR spectra were modeled using calculations based on the existence of silver nanoparticles in the form of prolate spheroids. The main advantage of our preparation method is that the metal nanoparticles are encapsulated in a-C from the beginning and this layer acts as an efficient chemical barrier.     

Synthesis of Mn doped ZnO nanocrystals by solvothermal route and its characterization

Undoped and Manganese doped Zinc Oxide were prepared by solvothermal technique. The structural analysis was carried out using X-ray diffraction. It showed that the undoped Zinc Oxide and Manganese doped Zinc Oxide nanocrystals to exhibit hexagonal wurtzite structure. Grain sizes were estimated from Atomic Force Microscopy and Transmission Electron Microscopy images. The surface morphological studies from Scanning Electron Microscope, Transmission Electron Microscope and Atomic Force Microscope depicted spherical particles with formation of clusters. The magnetic behavior studied by Vibrating Sample Magnetometer indicated paramagnetic behaviour. Hyperfine splitting is observed using Electron Spin Resonance studies.     

Synthesis and characterization of Mn quantum dots by bioreduction with water hyacinth

The bio-reduction method is reported as a part of a complimentary self-sustained technology, where bioremediation and metal particle production are related. The use of the characterization methods in this self sustainable technique open the expectative to be used for several other elements and with other plants, which will be discussed. However, the particular case of Mn nanoparticles involves an important option to generate nanoparticles in the range of 1-4 nanometers with a well controlled size and with a structure based on an fcc-like geometry for the smallest clusters and with more complex arrays for cluster greater than four shells, which involves magnetic moments significantly related to their atomistic configuration. At the same time, the use of the characterization methods establishes the dependence of the nanoparticle's size on the pH conditions used during the synthesis; small clusters in the range of 1-2 nm were generated using pH=5, and it was shown that for the smallest aggregates, simple polyhedron shapes are stable.