Effects of stabilizing heat treatment on microstructures and creep behavior of Zn-10Al-2Cu-0.02Ti alloy

The microstructures of as-extruded and stabilizing heat-treated Zn-10Al-2Cu-0.02Ti alloys were observed by scanning electron microscopy,transmission electron microscopy,electron probe microanalysis and X-ray diffraction analysis techniques.The change in structure after heat treatment and its effects on room temperature creep behavior were investigated by creep experiments at constant stress and slow strain rate tensile tests.The results show that after stabilizing heat treatment（（350℃,30 min,water-cooling）＋（100℃,12 h,air-cooling））,the amount of α＋η lamellar structure decreases,while the amount of cellular and granular structure increases.The heat-treated Zn-10Al-2Cu-0.02Ti alloy exhibits better creep resistance than the as-extruded alloy,and the rate of steady state creep decreases by 96.9% after stabilizing heat treatment.

The Application of Thermomechanical Dynamics (TMD) to Thermoelectric Energy Generation by Employing a Low Temperature Stirling Engine

A thermoelectric generation Stirling engine (TEG-Stirling engine) is discussed by employing a low temperature Stirling engine and the dissipative equation of motion derived from the method of thermomechanical dynamics (TMD). The results and mechanism of axial flux electromagnetic induction (AF-EMI) are applied to a low temperature Stirling engine, resulting in a TEG-Stirling engine. The method of TMD produced thermodynamically consistent and time-dependent physical quantities for the first time, such as internal energy ℰ(t), thermodynamic work Wth(t), the total entropy (heat dissipation) Qd(t)and measure or temperature of a nonequilibrium state T˜(t). The TMD analysis produced a lightweight mechanical system of TEG-Stirling engine which derives electric power from waste heat of temperature (40˚CT100˚C) by a thermoelectric conversion method. An optimal low rotational speed about 30θ′(t)/(2π)60(rpm) is found, applicable to devices for sustainable, clean energy technologies. The stability of a thermal state and angular rotations of TEG-Stirling engine are specifically shown by employing properties of nonequilibrium temperature T˜(t), which is also applied to study optimal fuel-injection and combustion timings of heat engines.

Effect Mechanism of Structure-Changed Water on Heat Stability of Lysozyme

Based on the mechanism of the effect of hydration on the heat stability of lysozyme and the theory of water molecule clusters, the effect of structure-changed water on heat stability of lysozyme has been studied. The results obtained by differential scanning calorimetry (DSC) showed that the thermal denaturation temperature of lysozyme had been elevated 8.47 K through hydration of lysozyme with processed water whose structure had been changed so it was called "structured water" compared to ordinary water. The reason is that structured water changed the dipole moment of water molecules and easily formed cyclic water hexamer or cage-like water hexamer, so that the interacting force of maintaining three-dimensional conformation of lysozyme could be reinforced.

Heat stability of winter wheat depends on cultivars, timing and protective methods

Heat stress negatively affects wheat production in many regions of the world.At present,sensitivity to heat stress remains one of the least understood aspects of wheat genetics and breeding,and measures for preventing heat stress are understudied.In this study,we used three cultivars of winter wheat(GY2018,SL02-1 and SY20)to evaluate the effect of heat stress at different days after anthesis(DAA)on yield and quality.Heat stability of the cultivars were analyzed and evaluated for the effects of two kinds of regulators on wheat under heat stress conditions.Heat treatment at 7 DAA led to the most substantial reduction in yield while GY2018 had the best heat stability with respect to yield,and demonstrated the most positive effects on several quality traits including protein content,sedimentation volume and glutenin and gliadin contents.Heat treatment at 14 DAA had the least reduction in yield,while SY20 had the best heat stability with respect to yield and heat treatment had minimal effects on quality.Heat treatment at 21 DAA had only a limited effect on yield,while SL02-1 had the best heat stability with respect to yield,but it showed the most negative effects on quality.Stable time at 14 DAA and protein content at 21 DAA can be used as indicators for detecting the stability of quality under heat stress.Among the three studied cultivars,SY20 was the most sensitive to heat stress with the stable time decreasing from 26.4 to 9.1 min,a higher sedimentation volume at 7 DAA,and a lowerγ-gliadin content which increased 2.4-fold under high-temperature treatment.The addition of various regulators had different effects:potassium dihydrogen phosphate(KDP)was more protective of yield with heat stress at 7 DAA,while Duntianbao(DTB)had better effects on quality with heat stress at 21 DAA.

Heat Stability of HA Antigen in Influenza Virus Rapid Diagnosis Kit

[ Objective] The aim was to select protective agent of HA antigen of influenza virus. [ Method] H3N2 and H1 N1 subtype influenza virus were added into A - F groups to conduct accelerated test at 37 ℃and measure HA titer through hemagglutination test. t Result] Hemagglutination titers of H3 N2 and H, N1 subtype influenza virus were 20 and 32 in group A （ with PBS buffer solution） for 28 d; heat stability of HA antigen proved the best in group F （with BSA, fucose, proclin 300, triton 100） ; hemagglutination titers of HA antigen of H3N2 and H1 N1 subtype virus were 48 and 96 for 28 d. [ Conclusion] Components in group F were best in protection on HA antigen, which can be a candidate of protective agent.

Synthesis of barium mercaptides and application of antimony/barium mercaptides

Mercaptoacetic acid, isooctyl thioglycolate and barium hydroxide used as start materials, barium bis (2 ethylhexyl thioglycolate) (Ba(2EHTG) 2), barium thioglycolate (Ba(TG)) and barium bisthioglycolate (Ba(TG) 2) were synthesized. Their optimum synthetic techniques were discussed, and some physicochemical data were reported. Infrared spectroscopy and elemental analysis methods were used to identify the structures. They were put into PVC plastic products together with antimony tris (2 ethylhexyl thioglycolate) (Sb(2EHTG) 3) under the suitable compounding, and their heat stability to PVC was studied. It is shown that these barium mercaptides have remarkable synergisms with antimony mercaptides and the long term stabilizing effect of organoantimony stabilizer can be effectively improved, reducing the amount of antimony compounds so as to avoid the decrease of its stabilizing effect.

Geothermal investigation of the thickness of gas hydrate stability zone in the north continental margin of the South China Sea

The exploration of unconventional and/or new energy resources has become the focus of energy research worldwide,given the shortage of fossil fuels.As a potential energy resource,gas hydrate exists only in the environment of high pressure and low temperature,mainly distributing in the sediments of the seafloor in the continental margins and the permafrost zones in land.The accurate determination of the thickness of gas hydrate stability zone is essential yet challenging in the assessment of the exploitation potential.The majority of previous studies obtain this thickness by detecting the bottom simulating reflectors（BSRs） layer on the seismic profiles.The phase equilibrium between gas hydrate stable state with its temperature and pressure provides an opportunity to derive the thickness with the geothermal method.Based on the latest geothermal dataset,we calculated the thickness of the gas hydrate stability zone（GHSZ） in the north continental margin of the South China Sea.Our results indicate that the thicknesses of gas hydrate stability zone vary greatly in different areas of the northern margin of the South China Sea.The thickness mainly concentrates on 200–300 m and distributes in the southwestern and eastern areas with belt-like shape.We further confirmed a certain relationship between the GHSZ thickness and factors such as heat flow and water depth.The thickness of gas hydrate stability zone is found to be large where the heat flow is relatively low.The GHSZ thickness increases with the increase of the water depth,but it tends to stay steady when the water depth deeper than 3 000 m.The findings would improve the assessment of gas hydrate resource potential in the South China Sea.

Switchable Dielectric Materials Based on 2-Methylimidazole

Two novel coordination polymers with molecular structures（2MI）＋[Zn（2MI）Cl3]-（1） and（2MI）＋NO3-（2） based on ligand 2-methylimidazole（2MI） were synthesized under solution method. Compound 1 crystallizes in the monoclinic system, space group Cc with a=7.489（2）, b=13.448（4）, c=13.983（4） , β=98.402（2）°, Z=4 and V=102.246（2） 3. Compound 2 crystallizes in the orthorhombic system, space group pnma with a=14.296（3）, b=6.3180（12）, c=7.3862（13） , β=90°, Z=4 and V=667.1（2） 3. Dielectric measurements show compounds 1 and 2 have reversible dielectric anomalous behaviors with variation frequencies at different temperature.

Synthesis and Characterization of Solid Electrolyte Ce_(0.95)Ca_(0.05)F_(2.95)

Polycrystalline Ce_(0.95)Ca_(0.05)F_(2.95) was prepared by a conventional solid-state reaction. The heat stability and ion conductivity of Ce_(0.95)Ca_(0.05)F_(2.95) were investigated by a high temperature calorimeter and an ac impedance technique. Experimental results indicate that Ce_(0.95)Ca_(0.05)F_(2.95) is stable at temperatures below 1000 K and represents the ionic conductivity of 1×10^(-3) to 10^(-1) Ω^(-1)·cm^(-1) in temperature range of 660 to 1180 K.

Effects of Stabilization Heat Treatment on Microstructure and Mechanical Properties of Si‑Bearing 15Cr–9Ni–Nb Austenitic Stainless Steel Weld Metal

Two 15Cr–9Ni–Nb austenitic stainless steel weld metals with 2.5%Si and 3.5%Si(namely 2.5Si and 3.5Si samples,respectively)were designed and prepared through tungsten inert gas(TIG)welding and then hold at 800℃ or 900℃ for 3 h for stabilization.The microstructure and mechanical properties were investigated both for the as-welded and after-stabilization heat treatment(SHT)weld metals.There are 3.0–4.0%martensite and 2.5–3.5%δferrite in the 2.5Si as-welded weld metal and 6.0–7.0%δferrite in the 3.5Si as-welded weld metal.After SHT,a large amount of martensite formed in the 2.5Si weld metal,andδ→γtransition occurred during the SHT process both for the 2.5Si and 3.5Si weld metals.There were a large amount of coarse NbC and few nanoscale NbC in the as-welded weld metal.During the SHT,a large amount of nanoscale NbC formed in the matrix,while a large number of G phases formed at the austenite grain boundaries and theδ/γinterfaces.The decrease in solid solution C andδferrite content led to the decline of the yield strength of the weld metal after SHT.The martensite formed in 2.5Si weld metal after SHT had less effect on strength because of its low carbon content.The G phases formed during the SHT reduced the impact energy of the weld metal because it promoted the intergranular fracture,while theδ→γtransition reduced the amount of theδ/γinterfaces and avoided the intergranular fracture,which was beneficial for the impact toughness of the weld metals.

Analysis of Biological Activity and Immunogenicity of Extracellular Products from Streptococcus iniae

[Objectives] This study aimed to analyze the biological activity and immunogenicity of extracellular products from Streptococcus iniae .[Methods] S. iniae was incubated with brain heart infusion agar medium （BHIA ＋ 4% calf serum） for 60 h. The bacterial liquid was rinsed with PBS, centrifuged, and filtered through microporous filtering film to collect extracellular products （ECPs）.[Results] Extracellular proteinase （ECPase） of S. iniae exhibited amylase, protease, lecitinase, gelatinase, lipase activities and hemolytic activity but had no urease activity. EDTA, DTT and PMSF could reduce ECPase activity to 72.4%, 77.6% and 72.4%, respectively. Cu^2＋ , Ca 2＋ , K^＋ and Mg^2＋ exhibited an inhibitory effect on ECPase activity, whereas Fe^3＋ , Co^2＋ and Mn^2＋ could activate ECPase activity. ECPs had good heat stability and exhibited relatively high activities under alkaline conditions. The optimal temperature for ECPs was 55 ℃. Two-dimensional electrophoresis was performed to analyze the main protein of ECPs. The results indicated that there are 12 main bands of ECPs, and the molecular weights mainly ranged between 28-68 kDa. About 120 protein spots were detected, and the molecular weights mainly ranged between 26-95 kDa. The mouse anti- S. iniae was used for Western-blot analysis of ECPs, and the results showed that there were four proteins, with molecular weights of 26, 37, 95, and 97 kDa, respectively. The pathogenicity assay indicated that ECPs of S. iniae were highly pathogenic to tilapia. The mortality rate of tilapia was enhanced as the concentration of ECPs increased.[Conclusions] This study provided a certain theoretical basis for revealing the pathogenic mechanism of Streptococcus iniae .

Local heat transfer properties in co- and counter-current G-L-S magnetically stabilized fluidized beds

Heat transfer coefficients were measured by immersed probes in co- and counter-current G-L-S magnetically stabilized fluidized beds （MSFBs） using air, water and nickel-alloy particles as the gas, liquid and solid phases. Influences of major factors, including magnetic field intensity, superficial gas and liquid velocities, liquid viscosity and surface tension, on heat-transfer properties were studied experimentally, indicating that both co- and counter-current G-L-S MSFB can provide relatively uniform radial distribution of heat transfer coefficients under appropriate operation conditions, thus controlling operation temperature for highly exothermic multi-phase reaction systems. Two correlations were provided to estimate accurately heat transfer properties in both co- and counter-current G-L-S MSFB systems, with an average error of less than 10%.

On the stability of the flow over a shrinking cylinder with prescribed surface heat flux

This study investigates the steady stagnation point flow and heat transfer passes a horizontal shrinking permeable cylinder.The free stream velocity and the prescribed surface heat flux arc assumed to vary linearly with the distance from a fixed point on the cylinder.The partial differential equations governing the flow and heat transfer are transformed into a system of ordinary differential equations via similarity transformation.These equations are solved numerically for several values of the governing parameters,such as suction parameter s,curvature parameter γ,and shrinking parameter λ.The equations arc solved numerically by employing the boundary value problem solver package available in MATLAB software,bvp4c.The effects of the governing parameters on the skin friction coefficient,surface temperature,velocity,and temperature profiles are examined.Given the existence of dual solutions in the present study for a certain range of the curvature parameter,stability analysis is carried out to determine which one of the solutions is stable as time passes.The outcome of the stability analysis demonstrates that only the first solution,with lower boundary layer thickness,appeared to be stable and thus physically reliable,while the other is not.It is also discovered that the boundary layer separation is delayed by reducing the curvature parameter.

High-temperature dielectric and microwave absorption performances of TiB2/Al2O3 ceramics prepared by spark plasma sintering

TiB_(2)/Al2O3 ceramics reinforced with Mg O are prepared by spark plasma sintering(SPS).The dielectric and microwave(MW)absorption properties are discussed.The results indicate that both the commercial TiB_(2)(C-TiB_(2))content and preparing temperature play important roles in the dielectric properties.Simultaneously,TiB_(2)/Al2O3 composite shows the best MW absorption property when the C-TiB_(2)content and preparing temperature are 9 wt%and 1400°C.To further improve the MW absorption properties,the composite containing 9 wt%synthesized TiB_(2)(S-TiB_(2))has been sintered at 1400°C.Its high-temperature complex permittivity is greater than that of TiB_(2)/Al2O3 composite with 9 wt%C-TiB_(2)sintered at 1400°C and is directly proportional to the temperature.Besides,TiB_(2)/Al2O3 composite with 9 wt%S-TiB_(2)possesses a better MW absorption at 25–500°C,its effective absorption bandwidth(RL<-5 dB)can reach 4.2 GHz at 25–500°C.And the minimum reflection loss(RLmin)value reaches-43.41 dB at the temperature of 800°C with a thickness of 1.45 mm for TiB_(2)/Al2O3 composite with 9 wt%C-TiB_(2).Consequently,the satisfying absorbing layer(d<1.75 mm),flexural strength,heat stability and considerable high-temperature MW absorption ability grant TiB_(2)/Al2O3 ceramics practical applications as high-temperature microwave absorption materials(MAMs).

Structural Modification of Al65Cu16.5Ti18.5 Amorphous Powder through Annealing and Post Milling： Improving Thermal Stability

To improve thermal stability of the Al65Cu16.5Ti18.5 amorphous powder,structural modification of the amorphous powder was performed through annealing and post milling.Annealing above the crystallization temperature（Tx） not only induced nanoscale intermetallics to precipitate in the amorphous powder,but also increased Cu atomic percentage within the residual amorphous phase.Post milling induced the amorphization of the nanocrystal intermetallics and the formation of Cu9Al4 from the residual amorphous phase.Thus,a mixed structure consisting of amorphous phase and Cu9Al4 was obtained in the powder after annealing and post milling（the APMed powder）.The phase constituent in the APMed powder did not change during the post annealing,which exhibited significantly improved thermal stability in comparison with the as-milled amorphous powder.

Microstructural and mechanical properties of ZA10 alloy tubes and their weld seams prepared by Conform continuous extrusion

In the present work,Zn-10 Al-2 Cu-0.05 Ti(ZA10)alloy tubes with a diameter of 12.5 mm and wall thickness of 1.2 mm were fabricated by one-pass and double-pass Conform continuous extrusion.A stabilizing heat treatment[350℃,30 min(furnace cooling)+120℃,12 h(air cooling)]was also applied to some of the double-pass tubes to improve the quality of their weld seams.The yield strength,ultimate tensile strength,elongation and expansion ratio of the one-pass continuous extrusion tube were 268.4 MPa,294.3 MPa,13.8%and 5.5%,respectively.Double-pass continuous extrusion improved these values to 278.4 MPa,317.2 MPa,15.4%and 11.4%,respectively.Double-pass tubes also had fewer aggregations of Al-αprecipitates along the welding seam,which improved seam quality and caused cracks to appear in the matrix,away from the weld-affected zone,during expansion testing.Heat-treated double-pass tubes exhibited superior yield strength(283.9 MPa)and ultimate tensile strength(328.5 MPa)but lower elongation(10.2%)and expansion ratios(10.3%).Additionally,the heat-treated tubes exhibited markedly lower elongation at room temperature due to the remarkable blockage of dislocation motions by fine-scale lamellar(α+η)eutectoid structures and a lower size effect when stretched.