Effect of hydrophilic silica nanoparticles on hydrate formation: Insight from the experimental study

Invasion of drilling fluid into natural gas hydrate deposits during drilling might damage the reservoir,induce hydrate dissociation and then cause wellbore instability and distortion of the data from well logging. Adding nanoparticles into drilling fluid is an effective method in reducing the invasion of drilling fluid and enhancing borehole stability. However, the addition of nanoparticles might also introduce hydrate formation risk in borehole because they can act as the "seeds" for hydrate nucleation. This paper presents an experimental study of the effect of hydrophilic silica nanoparticle on gas hydrate formation in a dynamic methane/liquid-water system. In the experiment, the ultrapure water with and without1.0 wt%–6.0 wt% concentrations of silica nanoparticles, grain sizes of 20 and 50 nm, were pressurized by methane gas under varied conditions of temperature and pressure. The induction time, the gas consumption, and the average rate of gas consumption in the system were measured and compared to those in ultrapure water. The results show that a concentration of 4.0 wt% hydrophilic SiO_2 particles with a grain size of 50 nm has a relatively strong inhibition effect on hydrate formation when the initial experimental condition is 5.0 °C and 5.0 MPa. Compared to ultrapure water, the hydrophilic nano-SiO_2 fluid increases the induction time for hydrate formation by 194% and decreases the amount and average rate of hydrate formation by 10% and 17%, respectively. This inhibition effect may be attributed to the hydrophilicity,amount and aggregation of silica nanoparticle according to the results of water activity and zeta potential measurements. Our work also elucidates hydrophilic, instead of hydrophobic, nanoparticles can be added to the drilling fluid to maintain wellbore stability and to protect the hydrate reservoir from drilling mud damage, because they exhibit certain degree of hydrate inhibition which can reduce the risk of hydrate reformation and aggregation during gas hydrate or deep water drilling if their concentration can be controlled properly.

Enhancing corrosion resistance of ZK60 magnesium alloys via Ca microalloying: The impact of nanoscale precipitates

Enhancing corrosion resistance of Mg-Zn alloys with high strength and low cost was critical for broadening their large-scale practical applications. Here we prepared solutionized, peak-and over-aged ZK60 alloys with and without microalloying Ca(0.26 wt.%) to explore the effects of nanoscale precipitates on their corrosion behavior in detail via experimental analyses and theoretical calculations. The results suggested the peak-aged ZK60 alloy with Ca addition showed improved corrosion resistance in comparison with the alloys without Ca,owing to the contribution of Ca on the refinement of precipitates and increase in their number density. Although the precipitates and Mg matrix formed micro-galvanic couples leading to dissolution, the fine and dense precipitates could generate “in-situ pinning” effect on the corrosion products, forming a spider-web-like structure and improving the corrosion inhibition ability accordingly. The pinning effect was closely related to the size and number density of precipitates. This study provided important insight into the design and development of advanced corrosion resistant Mg alloys.

Adsorption and Diffusion Behavior of Cl^- on Sputtering Fe–20Cr Nanocrystalline Thin Film in Acid Solution(pH = 2)

The adsorption and diffusion behavior of Cl^- on sputtering Fe-20 Cr nanocrystalline（NC） thin film compared with corresponding coarse crystalline（CC） alloy has been studied in HCl ＋ NaCl solution（pH = 2,[Cl^-]=0.1 mol/L） by electrochemical techniques,X-ray photoelectron spectroscopy（XPS） and the firstprinciples calculations.The XPS results show that adsorption and diffusion of Cl^- in the passive film has been inhibited on NC thin film.Ultra-violet photoelectron spectroscopy（UPS） results show that the work function Φ s of NC thin film（4.7 eV） is higher than that of CC alloy（4.5 eV）.The theoretical calculations and valence electron structure analysis were used to understand the effect of nanocrystallization in this work.

High strength-ductility and rapid degradation rate of as-cast Mg-Cu-Al alloys for application in fracturing balls

Specially designed Mg-Cu-Al alloys were prepared for the application in fracturing balls.In comparison to Mg-2.5 Cu alloy,Mg-2.5 Cu-6.0 Al alloy exhibits an improved compressive strength of 378 MPa and compressive strain of 27%,combined with a high degradation rate of 383 mm/y.Two kinds of second-phases are found in Mg-Cu-Al alloys,i.e.MgAlCu andβ-Mg_(17)Al_(12)+Al_(2)Cu phases.They form a discontinuous network and act as cathodes for micro-galvanic corrosion,leading to a high degradation rate.Moreover,the addition of Al could improve the strength and ductility simultaneously in Mg-Cu alloys.The enhancement of strength primarily arises from the solid-solution strengthening and second-phase hardening.A high density of basal,non-basal dislocations and stacking faults were activated upon mechanical deformation.This accounts for the good ductility in Mg-Cu-Al alloys.

JAMIP:面向材料基因工程研究的功能材料设计开源软件

材料信息学或材料基因工程作为新兴的材料研究与设计范式,通过深度结合材料大数据与人工智能机器学习算法,正在加速新材料、新功能和新原则的创新发现.如何高效产生、收集、管理、学习和挖掘大规模材料数据是开展材料信息学或材料基因工程研究的关键.JAMIP(Jilin Artificial-intelligence-aided Materials-design Integrated Package)材料设计软件为满足这方面的研究需求而设计,涵盖半导体材料、介电材料、金属材料等材料体系,为基于功能材料大数据与机器学习算法结合的新材料发现和设计提供工具支撑.软件基于Python语言开发,代码开源,既可以基于结构原型数据库高效开展大规模高通量材料计算,也可以实现对计算任务更精细的控制及新任务流程的灵活定制.软件包主体框架包含以高通量材料计算为核心的数据产生、数据收集、管理工具及数据存储、机器学习/数据挖掘等功能模块.机器学习模块集成了数据预处理、数据特征工程,以及常用机器学习算法的模型构建和性能评估子模块.软件各模块之间高度融合,能够高效产生、分析、管理和学习计算材料大数据,为开展材料信息学或材料基因工程研究、实现新材料设计提供专业化的操作软件平台.

基于激发依赖性钙钛矿/聚合物薄膜的紫外可视化研究

紫外可视化技术在安全监控、空间通信、物联网健康监测可穿戴设备等领域有着广泛的应用.由于其显著的光电特性,钙钛矿材料被认为是有前途的紫外光探测和成像的候选者.本文报道了具有激发依赖特性的钙钬矿/聚合物薄膜,通过改变紫外激发波长(260~380 nm)实现了从绿色到品红的动态可调荧光显示.通过探究不同聚合物基质、卤素比例和钙钛矿材料的阳离子对动态的多色紫外可视化的影响和理论计算,结果表明其荧光变化机理与钙钛矿材料中的氯空位有关.该钙钛矿/聚合物薄膜还可以通过丝网印刷工艺实现紫外可视化的图案化多色显示.该技术可能应用于物联网的信息安全、紫外可视化和动态多色显示.