共查询到17条相似文献,搜索用时 328 毫秒
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为了研究羟基磷灰石HA纳米微粒对低温保护剂玻璃化性质的影响,利用DSC测量了含有不同粒径(20nm,40nm,60nm)和不同质量浓度(0.1%,0.2%,0.4%,0.8%)HA纳米微粒的PEG-600(50%,w/w)溶液的玻璃化温度。试验结果表明:加入40nm,0.8%HA的PEG-600溶液的玻璃化转变温度最大,熔融温度最小,稳定性也最高。与未加纳米微粒的PEG-600溶液相比,玻璃化转变温度提高了5℃,熔融温度降低了4.5℃,稳定性提高了近30%。加入60nm,0.8%HA的PEG-600溶液的玻璃化转变温度和反玻璃化温度都是最小,而熔融温度最大,稳定性也最低。与未加纳米微粒的PEG-600溶液相比,反玻璃化温度降低了4.5℃,稳定性降低了14%。 相似文献
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利用差示扫描量热仪(Pyrid-Diamond DSC),研究乙二醇(EG)和丙三醇水溶液加入0.1%、0.5%质量分数,20nm、40nm、60nm粒径的HA纳米微粒后的过冷度、水合性质,分析HA纳米微粒对线性多元醇水溶液这些特性的影响。实验表明,纳米微粒加入后,线性多元醇水溶液过冷度显著降低,并随纳米微粒粒径增大而减小。水合实验的结果表明,HA纳米微粒对多元醇水溶液的水合性质影响显著,与未加入HA纳米微粒的线性多元醇溶液相比,纳米低温保护剂结晶焓降低,结合水含量增大。 相似文献
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《工程热物理学报》2015,(1)
To study the effects of Hydroxyapatite(HA) nanoparticles on devitrification in cryoprotectant solutions,the crystallization of glycerol(60%,w/w) and PEG-600(50%,w/w) solutions with HA nanoparticles of different sizes(20 nm、 40 nm、60 nm)and different concentrations(0.1%、 0.5%)during warming were investigated by using differential scanning calorimetry(DSC) combined with cryomicroscopy.Experimental results showed that the presence of nanoparticles does not change the glass transition temperatures and melting temperatures of quenched solutions,but affects the behavior of devitrification and recrystallization upon warming.The morphologies of glycerol and PEG-600 solutions are dendritic and spheric respectively,and the structures are not changed by adding nanoparticles.The ice fraction of glycerol solution containing 0.1%60nm HA nanoparticles diminished significantly when comparing to the control solution.The ice fractions of PEG-600 solutions increased dramatically between-64℃ and-54℃.The findings have significant implications for biomaterial cryopreservation. 相似文献
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抑制共晶产生对低温保存非常重要。本文利用差示扫描量热法研究了加低温保护剂(DMSO、乙二醇、 1,2丙二醇、甘油和1,3丁二醇)的NaCl水溶液的共晶行为。得到以5%、10%、15%NaCl水溶液为母液的五种保护剂溶液热流曲线图。研究发现,溶液共晶是过冷、随机过程。低温保护剂有抑制NaCl水溶液共晶的作用。低温保护剂浓度越高, 共晶焓越小,对共晶的抑制作用越大。不同种类保护剂的抑制共晶的能力从强到弱依次是甘油、乙二醇、 DMSO、 1,2 丙二醇和1,3丁二醇。升温过程中,溶液发生共晶反玻璃化现象和玻璃化现象。 相似文献
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我们用柠檬酸溶胶凝胶法成功制备了Pr掺杂La1-xPrxCrO3(x=0~0.6)纳米晶.在硝酸盐溶液中加入柠檬酸作为螯合剂,乙二醇为分散剂,得到干凝胶并在烧结温度为600 ℃时获得纯相钙钛矿结构纳米晶粉体,颗粒直径大约为40 nm且大小分布均匀.La0.5Pr0.5CrO3在场冷条件下的磁化强度以及在7K时的磁滞回线的测量结果表明,在260 K表现出顺磁到反铁磁转变,在200 K时磁化率达到最大值,随后磁化率随着温度的降低而急剧减小,在大约94 K的时候磁化率为0,随着温度的进一步降低,磁化率为负值. 相似文献
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Starowicz M Starowicz P Zukrowski J Przewo?nik J Lemański A Kapusta C Bana? J 《Journal of nanoparticle research》2011,13(12):7167-7176
We present a novel and facile method enabling synthesis of iron oxide nanoparticles, which are composed mainly of maghemite according to X-ray diffraction (XRD) and Mössbauer spectroscopy studies. The proposed process is realized by anodic iron polarization in deaerated LiCl solutions containing both water and ethanol. Water seems to play an important role in the synthesis. Morphology of the product was studied by means of transmission electron microscopy and XRD. In the solution containing almost 100% of water a black suspension of round shaped maghemite nanoparticles of 20–40 nm size is obtained. Regulating water concentration allows to control nanoparticle size, which is reduced to 4–6 nm for 5% of water with a possibility to reach intermediate sizes. For 3% or lower water concentration nanoparticles are of a needle-like shape and form a reddish suspension. In this case phase determination is problematic due to a small particle size with the thickness of roughly 3 nm. However, XRD studies indicate the presence of ferrihydrite. Coercivities of the materials are similar to those reported for nanoparticle magnetite powders, whereas the saturation magnetization values are considerably smaller. 相似文献
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Stable hydroxyapatite (HAP) nanoparticles system was synthesized from Ca(H(2)PO(4))(2) aqueous solution and saturated Ca(OH)(2) aqueous solution by an improved precipitation method. This method was reformed through using ultrasound irradiation as assistant technology due to its unique chemical reaction effects and adding glycosaminoglycans (GAGs) as regulation additive due to its strong interaction with HAP. The products were characterized by Malvern Zetasizer 3000HS Analysis system, TEM and ED. The size distribution and zeta potential of HAP nanoparticles were influenced by the concentration of GAGs. With the GAGs concentration of 0.35g/L, the better excellent HAP nanoparticle system could be obtained with the number-averaged particle size of 22.2nm in 84.5% area and 54.6nm in 15.5% area between 18.1nm and 117.4nm and the zeta potential of -60.9mV. In the presence of GAGs, the particle size and size distribution are little sensitive to the ultrasound irradiation (UI) time. With the increasing of UI time from 0.5h to 3h and 5h, the particle size increased a little and the crystallinity was improved. GAGs inhibited HAP crystal growth and stabilized HAP nanoparticles. Based on the TEM observation and size distribution determination of HAP nanoparticles, the possible formation mechanism of HAP nanoparticles stabilized by GAGs under UI was discussed. 相似文献
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The effects of liquid environment on nucleation, growth and aggregation of gold nanoparticles were studied. Gold nanoparticles
were prepared by pulsed laser ablation in deionised water with various concentrations of ethanol and also in pure ethanol.
UV/visible extinction and TEM observations were employed for characterization of optical properties and particle sizes respectively.
Preparation in water results in smaller size, shorter wavelength of maximum extinction and stable solution with an average
size of 6 nm. Nanoparticles in solution with low concentration ethanol up to 20 vol% are very similar to those prepared in
water. In the mixture of deionised water and 40 up to 80 vol% ethanol, wavelength of maximum extinction shows a red shift
and mean size of nanoparticles was increased to 8.2 nm. Meanwhile, in this case, nanoparticles cross-linked each other and
formed string type structures. In ethanol, TEM experiments show a mean size of 18 nm and strong aggregation of nanoparticles.
The data were discussed qualitatively by considering effects of polarity of surrounding molecules on growth mechanism and
aggregation. This study provided a technique to control size, cross-linking and aggregation of gold nanoparticles via changing
the nature of liquid carrier medium. 相似文献
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Size-controlled chemical reduction synthesis of nanostructured Cu was studied in the presence of a single modifier such as polyethylene glycols, sodium dodecyl benzene sulfonate, sodium dodecyl sulfate or a mixture of two different types of modifiers. The Cu nanoparticles were characterized by powder X-ray diffraction, transmission electron microscopy, selected area electron diffraction and Fourier transform infrared spectroscopy. The average particle size and particle size distribution of the nanostructured Cu depend upon the type of modifiers and the modifier effect follows the order: PEG-2000 > SDBS > PEG-600 > SDS > PEG-6000. The experimental results indicate that due to the existence of a synergistic action, a mixture of two types of modifiers has a significant effect on the particle size and the size distribution of Cu nanoparticles. 相似文献
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Zhen Fang Hassane Assaaoudi Hanbai Lin Xiaoming Wang Ian S. Butler Janusz A. Kozinski 《Journal of nanoparticle research》2007,9(4):683-687
Nanocrystalline SnO2 was synthesized in supercritical water at 385–415°C and 30 MPa (38–106 s residence time) in a tubular flow reactor from an
aqueous solution of 0.1–0.4 M SnCl4. The conversion rate was between 53 and 81%, but increased to 97.8% when 0.1 M NaOH was added. Nanoparticles were analyzed
by a series of independent analytical techniques, including TEM, Raman, XRD, SEM, EDX and FT-IR. The initial size of the particles
was about 3.7 nm. After calcination at 450°C for 2 h, the particle size increased to 4 nm. The particles were of low crystallinity,
as indicated by the weak Raman and XRD signals. All particles were composed of Sn and O, as verified by the EDX spectra. The
crystals were tetragonal, as confirmed by the weak XRD spectrum. After calcination at 600°C for 10 h, the particle size increased
to 9 nm, while high crystallinity was confirmed by Raman and XRD analyses. All the crystals had the same structure, as indicated
by TEM electron diffraction patterns. Using this one-step supercritical water process, nanoparticles of SnO2 can be conveniently produced continuously in a flow reactor in less than 2 min. 相似文献
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Tomáš Gbur Václav Čuba Viliam Múčka Martin Nikl Karel Knížek Milan Pospíšil Ivo Jakubec 《Journal of nanoparticle research》2011,13(10):4529-4537
Preparation of zinc oxide nanoparticles from aqueous solutions containing zinc nitrate or formate using UV irradiation was
investigated. Analysis of solid phase formed during irradiation confirmed the presence of zinc oxide or zinc peroxide nanoparticles
ranging in size from 1 to 70 nm, depending on initial precursors. Annealing at temperatures 650–1000 °C results in forming
of rice-like zinc oxide particles, up to hundreds of nm in size. Photochemical method yields material with high chemical purity
and uniform particle size distribution. In addition, photo-induced doping of zinc oxide with lanthanum was studied. Presence
of lanthanum in zinc oxide crystal lattice and post-preparation treatment in reduction atmosphere significantly increase the
UV excitonic luminescence at 395 nm in radioluminescence spectra. 相似文献
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Electrochemical method for the synthesis of silver nanoparticles 总被引:1,自引:0,他引:1
Rashid A. Khaydarov Renat R. Khaydarov Olga Gapurova Yuri Estrin Thomas Scheper 《Journal of nanoparticle research》2009,11(5):1193-1200
The article deals with a novel electrochemical method of preparing long-lived silver nanoparticles suspended in aqueous solution
as well as silver powders. The method does not involve the use of any chemical stabilising agents. The morphology of the silver
nanoparticles obtained was studied using transmission electron microscopy, scanning electron microscopy, atomic force microscopy
and dynamic light scattering measurements. Silver nanoparticles suspended in water solution that were produced by the present
technique are nearly spherical and their size distribution lies in the range of 2 to 20 nm, the average size being about 7 nm.
Silver nanoparticles synthesised by the proposed method were sufficiently stable for more than 7 years even under ambient
conditions. Silver crystal growth on the surface of the cathode in the electrochemical process used was shown to result in
micron-sized structures consisting of agglomerated silver nanoparticles with the sizes below 40 nm. 相似文献