“纳米乳液的制备、表征及粒径调控”实验的课程思政设计

将化学竞赛成果转化为具有农业特色的实验项目“纳米乳液的制备、表征及粒径调控”,并引入到物理化学实验教学中。通过实验使学生掌握纳米乳液的制备表征方法并研究制备因素对性质的影响,推动了农科和理科的融合渗透,培养了学生的跨学科思维,提高了科学素养。引导学生深刻认识纳米乳液对于减少农药使用量、保护生态环境的重要意义,关注国家粮食安全和食品安全等战略需求,加强了学生的绿色发展意识,激发了学生服务三农的责任感。

新农科背景下农业特色化学类专业建设的研究与实践

新农科背景下的人才培养对化学类专业建设提出更高要求,本文分析了化学类专业面对国家农业发展战略需求急需解决的问题,研究出解决问题的核心要素,凝练教学理念,设计农业特色化学类专业人才培养“中农大方案”,围绕提升“知农爱农情怀”和“强农兴农本领”重构了课程教学体系和实验实践教学体系,探索了加强思政育人和知农型教师队伍建设的新路径,培养了农林院校特色创新型领军后备人才。

新农科背景下竞赛成果深度融入化学实验教学的探索与实践

新农科背景下将我校具有农业特色的化学竞赛成果深度融入表面及胶体化学实验教学,有机结合思政元素,在实验内容设计和教学模式方面进行探索与实践,形成“竞赛成果馈赠教学-教学激励竞赛”的良性循环链条,建立实验教学内容更新的长效机制,树立学生爱农情怀,推动兼具农业知识和化学知识的复合型人才的培养。

化学实验教学中加强诚信教育的探索与实践

诚信是立德树人的重要内容,关系到大学生的成才与社会发展。化学实验课程的特点有利于诚信教育的开展,为了充分了解大学生的诚信意识及实验教学中是否存在诚信缺失等问题,我们开展了相关的问卷调查。综合调查结果及教学过程中的观察,总结出目前实验教学中存在的失信问题,并针对这些问题在教学中进行了诚信教育实践。

新农科背景下农林院校物理化学课程建设的改革与实践

以中国农业大学物理化学课程建设为例,坚持学生主体地位,从课程发展现状和挑战出发,准确把握课程建设方向,主动进行教学方式改革,始终围绕课程内容、前沿科技、国家战略进行实践探索,致力于培养卓越农林人才,肩负起知农爱农、强农兴农的使命和担当。

Plastic-elastic Model for Water-based Lubrication Considering Surface Force

Water-based lubrication is an effective method to achieve superlubricity,which implies a friction coefficient in the order of 10−3 or lower.Recent numerical,analytical,and experimental studies confirm that the surface force effect is crucial for realizing water-based superlubricity.To enhance the contribution of the surface force,soft and plastic materials can be utilized as friction pair materials because of their effect in increasing the contact area.A new numerical model of water-based lubrication that considers the surface force between plastic and elastic materials is developed in this study to investigate the effect of plastic flow in water-based lubrication.Considering the complexity of residual stress accumulation in lubrication problems,a simplified plastic model is proposed,which merely calculates the result of the dry contact solution and avoids repeated calculations of the plastic flow.The results of the two models show good agreement.Plastic deformation reduces the local contact pressure and enhances the function of the surface force,thus resulting in a lower friction coefficient.

Micro Crack of Aluminum Sheet During Cold Rolling

The micro crack of aluminum sheet during cold rolling lubricated with emulsions is investigated. Experi-ments show that micro cracks occur after cold rolling process and this is attributed to various parameters, for instance, the thin oxide film formed at the sheet surface. The micro crack spacing thus becomes an important parameter which deserves more concerns. The aspect ratio of these micro cracks is then analyzed theoreti-cally, which takes into consideration of the oxide fracture process. The good agreement between the obser-vations and the theoretical predictions validates the analysis. The approach can shed some new lights on the mechanical process of aluminium sheet during cold rolling.

Combination of diketone and PAO to achieve macroscale oil-based superlubricity at relative high contact pressures

1-(4-ethylphenyl)-nonane-1,3-dione(0206)is an oil-soluble liquid molecule with rod-like structure.In this study,the chelate(0206-Fe)with octahedral structure was prepared by the reaction of ferric chloride and 1,3-diketone.The experimental results show that when using 0206 and a mixed solution containing 60%0206-Fe and 40%0206(0206-Fe(60%))as lubricants of the steel friction pairs,superlubricity can be achieved(0.007,0.006).But their wear scar diameters(WSD)were very large(532µm,370µm),which resulted in the pressure of only 44.3 and 61.8 MPa in the contact areas of the friction pairs.When 0206-Fe(60%)was mixed with PAO6,it was found that the friction coefficient(COF)decreased with increase of 0206-Fe(60%)in the solution.When the ratio of 0206-Fe(60%)to PAO6 was 8:2(PAO6(20%)),it exhibited better comprehensive tribological properties(232.3 MPa).Subsequent studies have shown that reducing the viscosity of the base oil in the mixed solution helped to reduce COF and increased WSD.Considering the COF,contact pressure,and running-in time,it was found that the mixed lubricant(Oil3(20%))prepared by the base oil with a viscosity of 19.7 mPa·s(Oil3)and 0206-Fe(60%)exhibited the best tribological properties(0.007,161.4 MPa,3,100 s).

A sulfonated modification of PEEK for ultralow friction

Polyether ether ketone(PEEK)is a widely used material for friction pairs due to its excellent mechanical strength,good wear resistance,and chemical inertness.However,some modifications are necessary when PEEK is used as a water-lubricated friction pair.In this study,a novel sulfonation method was developed to design a water-lubricated friction pair with ultralow friction,good wear resistance,and high loading capacity.PEEK powders were sulfonated using ClSO3H and sintered to form bulk plastic.The sulfonated PEEK(SPEEK)plastic exhibited good tribological properties.At a low sliding speed,the friction coefficient was smaller than 0.02 when a 3 wt% NaCl solution was used as the lubricant.The order of magnitude of the wear rate was as low as 10^(-8) mm^(3)/(N·m).The mechanism of friction reduction was mainly hydration lubrication.The negatively charged -SO_(3)^(-) groups on the friction pair can adsorb hydrated Na+cations by electrostatic interactions.These hydrated Na+cations have a high load capacity and low shearing resistance.The ultralow wear mechanism observed in this study is possibly due to ultralow friction properties of the friction pairs prepared through the proposed sulfonation and thermoforming procedures.

How to improve superlubricity performance of diketone at steel interface:Effects of oxygen gas

Achievement of steady and reliable super-low friction at the steel/steel contact interface,one of the most tribological systems applied for mechanical moving parts,is of importance for prolonging machine lifetime and reducing energy consumption.Here we reported that the superlubricity performance of the steel/steel sliding interface lubricated with tiny amounts of diketone solution strongly depends on the oxygen content in surrounding environment.The increase of oxygen not only significantly shortens the initial running-in time but also further reduces the stable coefficient of friction in superlubricity stage due to the enhancement of tribochemical reactions.On the one hand,more severe oxidation wear occurring at higher oxygen content facilitates material removal of the contact interface,lowering the contact pressure and the corresponding initial friction.On the other hand,the growth of iron ions during the shear process in high oxygen environment promotes the formation of chelate which acted as an effective lubricated film chemisorbed at the steel/steel friction interface to further lower the interfacial friction.The results provide a new opportunity to further optimize the tribological performance of diketone superlubricity system,especially towards the lubrication of mechanical engineering materials.

Investigations of the superlubricity of sapphire against ruby under phosphoric acid lubrication

In this study,we address the superlubricity behavior of sapphire against ruby(or sapphire against itself)under phosphoric acid solution lubrication.An ultra-low friction coefficient of 0.004 was obtained under a very high contact pressure,with a virgin contact pressure up to 2.57 GPa.Related experiments have indicated that the load,sliding speed,and humidity of the test environment can affect superlubricity to some degree,so we tested variations in these conditions.When superlubricity appears in this study a thin film is present,consisting of a hydrogen bond network of phosphoric acid and water molecules adsorbed on the two friction surfaces,which accounts for the ultra-low friction.Most significantly,the wear rate of the sapphire and ruby in the friction process is very slow and the superlubricity state is very stable,providing favorable conditions for future technological applications.

Hydrodynamic effect on the superlubricity of phosphoric acid between ceramic and sapphire

In this work,a super-low friction coefficient of 0.003 was found between a silicon nitride ball and a sapphire plate lubricated by phosphoric acid solution.The wear mainly occurred in the running-in period and disappeared after superlubricity was achieved.The friction coefficient was effectively reduced from 0.3 to 0.003 at a constant speed of 0.076 m/s,accompanied by a 12-nm-thickness film.The lubrication regime was indicated to change from boundary lubrication in the running-in period to elastohydrodynamic lubrication in the superlubricity period,which is also supported by the results of the friction coefficient versus sliding speed.In addition,the experimental results showed good agreement with theoretical calculations based on the elastohydrodynamic lubrication theory,suggesting a significant hydrodynamic effect of phosphoric acid on superlubricity.

Modified graphene as novel lubricating additive with high dispersion stability in oil

Graphene is a promising material as a lubricant additive for reducing friction and wear.Here,a dispersing method which combines chemical modification of graphene by octadecylamine and dicyclohexylcarbodiimide with a kind of effective dispersant has been successfully developed to achieve the remarkable dispersion stability of graphene in base oil.The stable dispersion time of modified graphene(0.5 wt%)with dispersant(1 wt%)in PAO-6 could be up to about 120 days,which was the longest time reported so far.At the same time,the lubricant exhibits a significant improvement of tribological performance for a steel ball to plate tribo-system with a normal load of 2 N.The coefficient of friction between sliding surfaces was~0.10 and the depth of wear track on plate was~21 nm,which decreased by about 44%and 90%when compared to pure PAO-6,respectively.Furthermore,the analysis of the lubricating mechanisms in regard to the sliding-induced formation of nanostructured tribo-film has been contacted by using Raman spectra and TEM.

Graphite-based solid lubricant for high-temperature lubrication

High-temperature solid lubricants play a significant role in the hot metal forming process.However,preparing high-temperature solid lubricant is formidably challenging due to the stern working conditions.Here we successfully develop a new type of eco-friendly high-temperature graphite-based solid lubricant by using amorphous silica dioxide,aluminum dihydrogen phosphate,and solid lubricant graphite.The solid lubricating coating exhibits excellent tribological properties with a very low friction coefficient and good wear protection for workpiece at high temperature under the air atmosphere.An array of analytical techniques reveals the existence of solid lubricant graphite in the lubricating coating after the high-temperature friction test.A synergistic effect between the protective surface film and the solid lubricant graphite is proposed to account for such superior lubricating performance.This work highlights the synergistic effect between the protection layer and the lubricant graphite and further provides the insight in designing the high-temperature solid lubricant.

Fine genetic mapping of the chromosome 11q23.3 region in a Han Chinese population:insights into the apolipoprotein genes underlying the blood lipid-lipoprotein variances

The unusual chromosome 11q23.3 harboring the apolipoprotein(APO)gene cluster has been well documented for its essential roles in plasma lipid-related traits and atherosclerotic cardiovascular diseases.However,its genetic architecture and the potential biological mechanisms underlying complex phenotypes have not been well assessed.We conducted a study for this target region in a Han Chinese population through a stepwise forward framework based on massive parallel sequencing,association analyses,genetic fine mapping,and functional interpretation.The present study identified new meaningful genetic associations that were not simply determined by statistical significance.In addition to the APOA5 gene,we found robust evidence of the genetic commitments of APOC3 and APOA1 to blood lipids.Several variants with high confidence were prioritized along with the potential biological mechanism interpretations in the wake of adaptive fine-mapping analyses.rs2849174 in the APOC3 enhancer was discovered with an unrivaled posterior probability of causality for triglyceride levels and could mediate APOC3 expression through enhancer activity modulated by a combination of histone modifications and transcription factor accessibility.Similarly,multiple lines of evidence converged in favor of rs3741297 as a causal variant influencing high-density lipoprotein cholesterol.Our findings provided novel insights into this genomic locus in the Chinese population.

Friction characteristics of floppy disks

This note presents the principle and structure of a tribological measure for floppy disks. The precision of the force measuring system is 1 mN in loading and 3×10-6 N in friction. The resolution of the film thickness between head and floppy disk is 0.5 nm in the vertical and 1.5 nm in the horizontal direction. in order to investigate the tribological characteristics of floppy disks, six types of floppy disks have been tested and the floating properties of these disks are also studied with film measuring system. The experimental results of the surface morphology and friction coefficient of these floppy disks using the atomic force microscope/friction force mcroscope (AFM/FFM) are in accordance with the conclusion made by our own measuring system. The experimental results show that the air film thickness between head and disk is of the same order as the surface roughness of floppy disks.

Ion energy-induced nanoclustering structure in a-C:H film for achieving robust superlubricity in vacuum

Hydrogenated amorphous carbon(a-C:H)films are capable of providing excellent superlubricating properties,which have great potential serving as self-lubricating protective layer for mechanical systems in extreme working conditions.However,it is still a huge challenge to develop a-C:H films capable of achieving robust superlubricity state in vacuum.The main obstacle derives from the lack of knowledge on the influencing mechanism of deposition parameters on the films bonding structure and its relation to their self-lubrication performance.Aiming at finding the optimized deposition energy and revealing its influencing mechanism on superlubricity,a series of highly-hydrogenated a-C:H films were synthesized with appropriate ion energy,and systematic tribological experiments and structural characterization were conducted.The results highlight the pivotal role of ion energy on film composition,nanoclustering structure,and bonding state,which determine mechanical properties of highly-hydrogenated a-C:H films and surface passivation ability and hence their superlubricity performance in vacuum.The optimized superlubricity performance with the lowest friction coefficient of 0.006 coupled with the lowest wear rate emerges when the carbon ion energy is just beyond the penetration threshold of subplantation.The combined growth process of surface chemisorption and subsurface implantation is the key for a-C:H films to acquire stiff nanoclustering network and high volume of hydrogen incorporation,which enables a robust near-frictionless sliding surface.These findings can provide a guidance towards a more effective manipulation of self-lubricating a-C:H films for space application.

Water-based superlubricity in vacuum

This study achieved water‐based superlubricity with the lubrication of H_3PO_4 solution in vacuum(highest vacuum degree <10–4 torr) for the first time by performing a pre‐running process in air before running in vacuum. The stable water‐based superlubricity was sustainable in vacuum(0.02 torr) for 14 h until the test was stopped by the user for non‐experimental factor. A further analysis suggested that the superlubricity may be attributed to the phosphoric acid–water network formed in air, which can efficiently lock water molecules in the liquid lubricating film even in vacuum owing to the strong hydrogen bond interaction. Such capability to lock water is strongly affected by the strength of hydrogen bond and environmental conditions. The realization of water‐based superlubricity with H_3PO_4 solution in vacuum can lead to its application in space environment.

Unlocking the secrets behind liquid superlubricity:A state-ofthe-art review on phenomena and mechanisms

Superlubricity,the state of ultralow friction between two sliding surfaces,has become a frontier subject in tribology.Here,a state-of-the-art review of the phenomena and mechanisms of liquid superlubricity are presented based on our ten-year research,to unlock the secrets behind liquid superlubricity,a major approach to achieve superlubricity.An overview of the discovery of liquid superlubricity materials is presented from five different categories,including water and acid-based solutions,hydrated materials,ionic liquids(ILs),two-dimensional(2D)materials as lubricant additives,and oil-based lubricants,to show the hydrodynamic and hydration contributions to liquid superlubricity.The review also discusses four methods to further expand superlubricity by solving the challenge of lubricants that have a high load-carrying capacity with a low shear resistance,including enhancing the hydration contribution by strengthening the hydration strength of lubricants,designing friction surfaces with higher negative surface charge densities,simultaneously combining hydration and hydrodynamic contribution,and using 2D materials(e.g.,graphene and black phosphorus)to separate the contact of asperities.Furthermore,uniform mechanisms of liquid superlubricity have been summarized for different liquid lubricants at the boundary,mixed,and hydrodynamic lubrication regimes.To the best of our knowledge,almost all the immense progresses of the exciting topic,superlubricity,since the first theoretical prediction in the early 1990s,focus on uniform superlubricity mechanisms.This review aims to guide the research direction of liquid superlubricity in the future and to further expand liquid superlubricity,whether in a theoretical research or engineering applications,ultimately enabling a sustainable state of ultra-low friction and ultra-low wear as well as transformative improvements in the efficiency of mechanical systems and human bodies.