Devitrification process in rapidly solidified Al-Ni-Cu-Nd metallic glass

In the present study, rapidly solidified ribbons of Al87 Ni7Cu3 Nd3 metallic glass was prepared by usingmelt spinning. Devitrification process of the totally amorphous ribbons was investigated by high temperature X-raydiffraction analysis, combining with differential scanning calorimetry, under continuous and isothermal heating re-gime. The X-ray diffraction intensity and full width at the half maximum (FWHM) were analyzed to investigate theincrease of crystallized amount and growth of α-Al crystal particles. The results show that under continuous heatingregime, the metallic glass devitrifies via two main stages: primary crystallization, resulting in two-phase mixture ofα-Al plus residual amorphous phase, and secondary crystallization, corresponding to rapid precipitation of some in-ter-metallic phases in the form of dispersion or eutectic mixture. Under isothermal heating regime, only Al crystalprecipitates from the Al-rich amorphous matrix at low temperature, and when heating at 280 ℃ only Al crystal pre-cipitates within a short time, and then Al8 Cu4 Nd forms, followed by Al3 Ni, in the residual amorphous phase. Whenheating at higher temperature or for longer time, Aln Nd3 forms, the amorphous phase disappears, and the ribbonsdevelop into polycrystalline morphologies with multiply phase mixture of a-Al, Al8 Cu4 Nd, Al3 Ni, and Al11 Nd3.

Research on Ice Crystal Growth Inside the Vitrified Vs55 with Magnetic Nanoparticles During Devitrification by Cryomicroscopy

The effect of magnetic nanoparticles(mNPs) on the devitrification crystallization of typical vitrification solution Vs55 was systematically explored by differential scanning calorimetry(DSC) and cryomicroscope system. The results show tliat,(i) the mNPs coated by both carboxylic acid(CA) and polyethylene glycol(PEG) had little effect on the glass transition temperature(rg) of Vs55, but had significant effect on the devitrification transition temperature(7a) and devitrification enthalpy(Hrd),(ii) in the range of the devitrification area(-85- 0℃), the MNPs coated by CA can significantly accelerate the devitrification of Vs55 as the isothermal temperatures and the cooling rates increased, and the ice growth rate was 0.37 p.m/s at the isothermal temperature of-85 ℃, and was about 2.19 gm/s at -75℃. Also, the ice growth rates rose from 1.72 pm/s to 3.54 pm/s when the cooling rates were increased from 2 ℃/min to 100 ℃/min(at the isothennal temperature of -75℃),(iii) magnetic nanoparticles coated by both PEG and CA could promote the devitrification of Vs55, for instance, without any crystal growth inside Vs55 at the isothermal temperature of-80℃, but 1.04 and 2.31 gm/s for adding magnetic nanoparticles coated by CA and PEG, respectively. Compared with the samples coated by CA, PEG promoted the devitrification of Vs55 in a much more positive way, and the ice growth rates were 0.62 and 6.25 μm/s at the isothermal temperatures of -85 and -75 ℃, respectively. Tliese results indicate that the surface coating of MNPs could significantly affect tlie recrystallization of Vs55, and further work should be conducted in the future research.

Effects of nanoparticles on devitrification and recrystallization of aqueous glycerol and PEG-600 solutions

Nanoparticles in solution offer unique electrical, mechanical and thermal properties due to their physical presence and interac- tion with the state of dispersion. This work is aimed to study the effects of hydroxyapatite （HA） nanoparticles on the behavior of devitrification and recrystallization of glycerol （60% w/w） and PEG-600 （50% w/w） solutions during warming. HA nano- particles of different sizes （20, 40, 60 nm） and concentrations （0.1%, 0.5%, w/w） were incorporated into solutions, and were studied by calorimetric analysis coupled with cryomicroscopy. The presence of HA nanoparticles has little effect on the devit- rification end temperatures, but affects the devitrification onset temperatures of glycerol and PEG-600 solutions. The investi- gation with the cryomicroscope observed that the ice morphologies of glycerol and PEG-600 solutions are dendritic and spher- ic respectively. The ice fraction of glycerol solution containing 0.1% HA with the size of 60 nm decreased to 2/5 of that of the solution without nanoparticles at -45℃. The ice fractions of PEG-600 solutions increased signifcantly between -64℃ and -54℃, and the ice fraction of PEG-600 solution without nanoparticles increased by 92% within the temperature range. The findings have significant implications for biomaterial cryopreservation, cryosurgery, and food manufacturing. The complexity of ice crystal growth kinetics in nanoparticle-containing solutions awaits further study.

Effects of Hydroxyapatite Nanoparticles on Devitrification Crystallization in Cryoprotectant Solutions

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.

Devitrification-induced an Ultrahigh Strength Al-based Composite Maintaining Ductility

A new Al-based composite consisting of submicron-sized α-Al matrix embedded with precipitated intermetallic phases was developed by controlling the devitrification process of an Al-Ni-Y-Co-La amorphous alloy.Such a homogeneous composite structure presented an ultrahigh strength of about 1.34 GPa and a large compressive plastic strain up to 22%.The unique mechanical properties during compression are mainly attributed to the dislocation slip deformation of ductile a-AI matrix and the shear-induced refinement of strengthening intermetallic phases.

Thermal and Structural Characterization of Transparent Rare-Earth Doped Lead Fluoride Glass-Ceramics

The devitrification of glasses with composition 50GeO2-40PbO-10PbF2-xREF3, RE = Gd, Eu, 0 3+: β-PbF2 nanocrystals embedded in a glassy oxide matrix. This transformation is investigated using thermal analysis, X-ray diffraction and electron microscopy. A comparison with RE3+: β-PbF2 ceramics prepared by standard ceramic techniques is performed. The Rare Earth cations show a strong nucleating effect for the precipitation of the RE3++: β-PbF2 nanocrystals. The evolution of the unit cell parameters of the REF3: β-PbF2 solid solution results from a combined effect of Pb2+-RE3+ substitution and interstitial F– introduction. In the glass ceramics, RE3+: β-PbF2 nanocrystals are constrained by the glassy matrix when they form with a pressure equivalent to 1.6 GPa. The constrained nanocrystals can return to a relaxed state by chemical dissolution of the embedding glassy matrix, followed by thermal treatments.

Reservoir space types and the factors influencing the characteristics of spherulite in rhyolite

Oil-gas reservoir space types involving spherulite in pyromeride rocks are common in the Lower Cretaceous Shangkuli Formation, the Hailar Basin, China. The main types include interspherulite fissures, interlayer fissures, intraspherulite concentric rings and net microcracks, cavity pores, dissolution pores, and devitrification pores. The first two were found to restrict the effective plane porosity of interspherulite. Devitrification microporosities, microcracks, cavity pores, and spherulite diameter influence the effective plane porosity of intraspherulite. The degree of dissolution is determined by the degree of development and the type of intraspherulite microcracks. Another important role of ring and net microcracks is to connect devitrification pores to form a pore and fissure network. Finally, chilling contraction plays an important role in the form and development of interspherulite fissures, microcracks, and cavity pores. The diameter of spherulite restricts chilling contraction, especially when the diameter is between the common spherulites and lithophysae, thus benefiting microcrack and cavity pore formation. To summarize, devitrification microporosities represent excellent oil reservoir space, while offering micro-channels for the movement of formation water and organic fluids. However, the inclusion of microcracks improves this capacity.