Tribological properties and tribomechanism of nickel nanoparticles in-situ synthesized in rapeseed oil

Nickel(Ni)nanoparticles can be enriched on the surface of iron-based frictional pairs,which provides the possibility to get rid of the competitive adsorption between the polar species of vegetable oil and the surface-active nano-additives thereon.In this paper,nickel acetylacetonate was used as a precursor to in-situ synthesize nickel nanoparticles with an average diameter of about 12 nm in rapeseed oil(RO)as the reducing agent,surface modifier,and solvent as well.The tribological properties of the as-synthesized Ni nanoparticles were evaluated with a four-ball tribometer,and their tribomechanism was investigated based on the characterizations of the tribofilm on rubbed steel surfaces by the scanning electron microscopy(SEM),transmission electron microscopy(TEM),and X-ray photoelectron spectroscopy(XPS).It was found that the Ni nanoparticles in-situ prepared in the RO with a mass fraction of 0.3%can reduce the wear scar diameter(WSD)of the steel ball by 36%.This is because,on the one hand,the Ni nanoparticles are adsorbed on the rubbed steel surfaces to repair or fill up the micro-pits and grooves thereon.On the other hand,Ni nanoparticles participate in tribochemical reactions with atmospheric O and steel substrate to form the tribochemical reaction film on the rubbed steel surfaces with the assistance of friction-induced heat and applied normal load.In addition,an amorphous carbon film is formed on the rubbed surface via the carbonization of base oil under the catalysis of Ni nanoparticles.The adsorbed Ni layer,the tribochemical reaction film,and the carbon layer comprise a composite tribofilm composed of amorphous carbon,polar fatty acid,metallic nickel,iron oxides,and nickel oxides on the rubbed steel surfaces,which contributes to significantly improving the antiwear ability and load-carrying capacity of the RO for the steel-steel sliding pair.

Self-dispersed molybdenum disulfide quantum dot/graphene crumpled ball as efficient high temperature lubricant additive

Inorganic nanoparticles have been proved as powerful lubricant additives at elevated temperature.However,the tribological properties are inevitably impaired due to poor dispersion and insufficient high temperature resistance of organic matter modified nanoparticles.Here,we prepare a self-dispersed molybdenum disulfide quantum dot/graphene crumpled ball(MGCB)comprising molybdenum disulfide quantum dot uniformly interspersed on the wrinkled graphene ball.The crumpled ball composite possesses excellent dispersity in polyalkylene glycol base oil without depending on surface modifiers.Compared with the conventional phosphate esters lubricant,our results indicate MGCB could vastly improve the lubrication performance of polyalkylene glycol with an extremely low concentration(0.05 wt%)at elevated temperature(150°C),showing a friction reduction of 47%and a wear reduction of 30%compared with the conventional phosphate esters lubricant(tricresyl phosphate,TCP).This is because crumpled ball potentiates synergistic lubrication effect within the boundary lubrication.Overall,we envision our designed self-dispersed MGCB has significant potential in tribological application at elevated temperature.

Study on the mechanism of rapid formation ofu ultra-thick tribofilm by CeO_(2)nano additive and ZDDP

CeO_(2)nanoparticles are potential anti-wear additives because of their outstanding anti-wear and load-bearing capacity.However,the shear-sintering tribo-film formation mechanism of oxide nanoparticles limits the tribo-film formation rate and thickness greatly.In this study,by compounding with zinc dioctyl dithiophosphate(ZDDP),ultra-fine CeO_(2)nanoparticles modified with oleylamine(OM)can quickly form 2μm ultra-thick tribo-film,which is 10-15 times thicker than that of ZDDP and CeO_(2),respectively.The ultra-thick tribo-film presents a nanocomposite structure with amorphous phosphate as binder and nano-CeO_(2)as filling phase,which leads to the highest loading capacity of composite additives.The results of adsorption experiments tested by dissipative quartz crystal microbalance(QCM-D)showed that the Ps value of additive has nothing to do with its equilibrium adsorption mass,but is directly proportional to its adsorption rate in 10 s.The compound additive of CeO_(2)and ZDDP presented the co-deposition mode of ZDDP monolayer rigid adsorption and CeO_(2)viscoelastic adsorption on the metal surface,which showed the highest adsorption rate in 10 s.It is found that the tribo-film must have high film forming rate and wear resistance at the same time in order to achieve super thickness.Cerium phosphate was formed from ZDDP and CeO,through tribochemistry reaction,which promotes the formation of an ultra-thick tribo-film with nanocomposite structure,which not only maintains the low friction characteristics of CeO,but also realizes high Pg and high load-carrying capacity.

俄罗斯新冠肺炎疫情的扩散:过程、格局与影响因素研究

遵循过程-格局-机理的脉络,结合每日新增病例、累计确诊病例、治愈量、死亡量等分析俄罗斯新冠肺炎疫情的发展过程,利用空间自相关分析研究俄新冠肺炎疫情的格局变化,基于多元线性回归分析探讨俄新冠肺炎疫情扩散的影响因素。研究发现:自2020年1月31日俄罗斯出现首例确诊病例以来,俄新冠肺炎疫情经历了平稳偶发、迅速暴发和扩散、扩散衰退、严重扩散等4个阶段,其治愈量保持稳定上升态势,死亡率徘徊于2%。人口规模、经济发展、医疗水平、交通设施等是影响俄罗斯新冠疫情扩散的重要因素,空间上,俄新冠肺炎疫情扩散表现为早期的多点扩散到后期的全面扩散,以及以莫斯科市为中心的邻近扩散、迁移扩散、廊道扩散的“由西到东”格局特征,与此同时,俄内部疫情也表现出一定的空间集聚性,莫斯科市、莫斯科州、圣彼得堡市、下诺夫哥罗德州、斯维尔德洛夫斯克州、汉特-曼西自治区、罗斯托夫州、克拉斯诺亚尔斯克边疆区等是疫情重灾区。最后总结了新冠肺炎疫情下的中俄未来合作发展对策与建议。

Perturbing tumor cell metabolism with a Ru(Ⅱ)photo-redox catalyst to reverse the multidrug resistance of lung cancer

The novel concept of enzyme photocatalysis has recently attracted much attention in developing anticancer therapy.However,the relationship between coenzyme depletion and cellular metabolomic changes has rarely been investigated.Herein,we report the rational design of a deep-red light-triggered bis-tridentate Ru(Ⅱ)photocatalyst(Ru3),which induces cell metabolism disorder to combat multidrug resistance.Ru3 exhibits promising multiple triplet excited states,a long lifetime,and high photocatalytic activity toward the coenzyme.Consequently,Ru3 shows high phototherapeutic activity(photo index=191–833)against diverse resistant(cisplatin,5-fluorouracil,or paclitaxel)lung cancer cells by inhibiting cellular peptide,lipid,and glycerophospholipid metabolism.We believe that cell metabolism inhibition by photo-redox catalysts is an effective form of therapeutics for drug-resistant cancer cells.

Sono-ReCORMs for synergetic sonodynamic-gas therapy of hypoxic tumor

Carbon monoxide(CO)gas therapy,a novel anti-tumor technique based on the cytotoxicity from the CO released in situ,has become one of the hot topics in cancer treatment.Since the technique is oxygenindependent,it displays promising therapeutic effect for hypoxic tumor where traditional photodynamic therapy shows limited efficacy and insufficient penetration depth.To fully address these limitations of PDT,we propose a synergetic sonodynamic-CO gas releasing strategy for the therapy of hypoxic tumor.In this work,two rhenium(Ⅰ)tricarbonyl complexes with different substituted ligands are investigated for US-triggered ROS generation and CO release.Our results indicated that the electron-donating NMe2-substituted complex(Re-NMe2)exhibits stronger luminescence intensity and generates more singlet oxygen(1O2)than the electron-withdrawing NO2-substituted complex(Re-NO2).In addition,Re-NMe2displays release of CO triggered by US,thus showing high sono-cytotoxicity to tumor cells in-vitro and in-vivo.The strong ROS-generating capability combined with rapid CO-releasing feature from Re-NMe2has made it a powerful tool for the efficient treatment of hypoxic tumor.

Synergistic tribological effect between polyisobutylene succinimide-modified molybdenum oxide nanoparticle and zinc dialkyldithiophosphate for reducing friction and wear of diamond-like carbon coating under boundary lubrication

Organic molybdenum lubricant additive like molybdenum dialkyl dithiocarbamate(MoDTC)can cause wear acceleration of diamond-like carbon(DLC)coating coupled with steel under boundary lubrication,which hinders its industrial application.Therefore,polyisobutylene succinimide(PIBS),an organo molybdenum amide,was adopted to modify molybdenum oxide affording molybdenum polyisobutylene succinimidemolybdenum oxide nanoparticles(MPIBS-MONPs)with potential to prevent the wear acceleration of DLC coating.The thermal stability of MPIBS-MONPs was evaluated by thermogravimetric analysis.Their tribological properties as the additives in di-isooctyl sebacate(DIOS)were evaluated with MoDTC as a control;and their tribomechanism was investigated in relation to their tribochemical reactions and synergistic tribological effect with zinc dialkyldithiophosphate(ZDDP)as well as worn surface characterizations.Findings indicate that MPIBS-MONPs/ZDDP added in DIOS can significantly reduce the friction and wear of DLC coating,being much superior to MoDTC.This is because MPIBS-MONPs and ZDDP jointly take part in tribochemical reactions to form a composite tribofilm that can increase the wear resistance of DLC coating.Namely,the molybdenum amide on MPIBS-MONPs surface can react with ZDDP to form MoS2 film with excellent friction-reducing ability;and MPIBS-MONPs can release molybdenum oxide nanoparticle to form deposited lubrication layer on worn surfaces.The as-formed composite tribofilm consisting of molybdenum oxide nanocrystal,amorphous polyphosphate,and molybdenum disulfide as well as a small amount of Mo2C accounts for the increase in the wear resistance of DLC coating under boundary lubrication.

Ultrasound-active ReCORM-AIEgen for gas and sonodynamic therapy of mycobacterium biofilms

Bacterial infection is the leading cause of many severe inflammation diseases. The development of novel and effective therapeutic approaches to counter bacterial infections, especially for drug-resistant bacteria, is essential. Herein, we have successfully developed an ultrasound-active tricarbonyl rhenium(Ⅰ) complex with tetraphenylethylene(TPE) modification(RePyTPE) for CO gas therapy and sonodynamic therapy of bacterial infections. RePy-TPE produced reactive oxygen species and released CO under ultrasound irradiation. In addition, RePy-TPE showed aggregation-induced emission in water due to the introduction of TPE, which enhanced the yield of ^(1)O_(2) generation in a biological aqueous solution. The produced ^(1)O_(2) and released CO killed mycobacterium smegmatis(M. smegmatis) and Escherichia coli(E. coli), as shown by bacterial membrane damage and biofilm elimination. Furthermore, ultrasound-active RePy-TPE perturbed the purine metabolism of the bacteria, which disturbed the biosynthesis of DNA and energy metabolism, eventually reducing the vitality of bacteria. This article provides a novel strategy for the development of ultrasound-active metal-based antibiotics.

Iridium photosensitizer constructed liposomes with hypoxia-activated prodrug to destrust hepatocellular carcinoma

Hypoxic tumor microenvironment is a major challenge for photodynamic therapy(PDT). To overcome this problem, PDT combined hypoxia-activated chemotherapy is a promising strategy for hypoxic cancer therapy. Herein, a multifunctional liposome(AQ4N-Ir1-sorafenib-liposome) is prepared by encapsulating a hypoxia-activated prodrug AQ4N, a photosensitizer iridium(III) complex and hepatocellular carcinoma(HCC) targeting drug sorafenib, for synergistic therapy of HCC. Ir1-mediated PDT upon irradiation induces ROS generation and hypoxic environment, which leads to the disassembly of the liposome and activates the antitumor activity of AQ4N. Meantime, the co-delivered sorafenib could effectively target therapy of HCC. It is noted that ferroptosis mechanism is proved during the treatment. This work contributes to the design of hypoxia-responsive multifunctional liposome for combination of chemotherapy, targeting therapy and PDT. It is a promising strategy for hypoxic HCC therapy.

Synthesis of water-soluble Cu nanoparticles and evaluation of their tribological properties and thermal conductivity as a water-based additive

Efficient and sustainable use of water-based lubricants is essential for energy efficiency.Therefore,the use of water-lubricated mechanical systems instead of conventional oil lubricants is extremely attractive from the viewpoint of resource conservation.In this study,water-soluble Cu nanoparticles of size approximately 3 nm were prepared at room temperature(around 25 °C) via in-situ surface modification.The tribological behavior of the as-synthesized Cu nanoparticles as an additive in distilled water was evaluated using a universal micro-tribotester.The results show that the as-synthesized Cu nanoparticles,as a water-based lubricant additive,can significantly improve the tribological properties of distilled water.In particular,the lowest friction coefficient of 0.06 was obtained via lubrication with a concentration of 0.6 wt% of Cu nanoparticles in distilled water,which is a reduction of 80.6% compared with that obtained via lubrication with distilled water alone.It is considered that some Cu nanoparticles entered the contact area of the friction pairs to form a complex lubricating film and prevent direct contact of the friction pairs.Furthermore,some Cu nanoparticles in the solution accelerate the heat transfer process,which also results in good tribological properties.

Effects of magnetic ionic liquid as a lubricant on the friction and wear behavior of a steel-steel sliding contact under elevated temperatures

A magnetic ionic liquid(abridged as MIL)[C_(6)mim]_(5)[Dy(SCN)_(8)]was prepared and used as the magnetic lubricant of a steel-steel sliding pair.The tribological properties of the as-prepared MIL were evaluated with a commercially obtained magnetic fluid lubricant(abridged as MF;the mixture of dioctyl sebacate and Fe_(3)O_(4),denoted as DIOS-Fe_3O_4)as a control.The lubrication mechanisms of the two types of magnetic lubricants were discussed in relation to worn surface analyses by SEM-EDS,XPS,and profilometry,as well as measurement of the electric contact resistance of the rubbed steel surfaces.The results revealed that the MIL exhibits better friction-reducing and antiwear performances than the as-received MF under varying test temperatures and loads.This is because the MIL participates in tribochemical reactions during the sliding process,and forms a boundary lubrication film composed of Dy_(2)O_(3),FeS,FeSO_(4),nitrogen-containing organics,and thioether on the rubbed disk surface,thereby reducing the friction and wear of the frictional pair.However,the MF is unable to form a lubricating film on the surface of the rubbed steel at 25°C,though it can form a boundary film consisting of Fe_(3)O_(4) and a small amount of organics under high temperature.Furthermore,the excessive Fe_(3)O_(4) particulates that accumulate in the sliding zone may lead to enhanced abrasive wear of the sliding pair.

Controllable synthesis of different morphologies of CuO nanostructures for tribological evaluation as water-based lubricant additives

In this study,water soluble CuO nanostructures having nanobelt,nanorod,or spindle morphologies were synthesized using aqueous solutions of Cu(NO_(3))_(2)·3H_(2)O and NaOH by adjusting the type of surface modifier and reaction temperature.The effect of morphologies of these various CuO nanostructures as water‐based lubricant additives on tribological properties was evaluated on a UMT‐2 micro‐friction tester,and the mechanisms underlying these properties are discussed.The three different morphologies of CuO nanostructures exhibited excellent friction‐reducing and anti‐wear properties.Tribological mechanisms differed in the initial stage of frictional interactions,but in the stable stage,a tribochemical reaction film and adsorbed lubricious film on the rubbing surfaces played important roles in hindering direct contact between friction pairs,leading to improved tribological properties.

Sonodynamic cancer therapy by novel iridium-gold nanoassemblies

Metal-based compounds with excellent photo-physical properties show good photochemotherapeutic performance.But,low in-depth tissue penetration of light limits their effectivity for deeply buried tumors.Encouraged by the sonosensitizing ability of the traditional organic photosensitizers,here,we developed AuNPs@Ir1 as a sonosensitizer by hybridizing an organometallic Ir(Ⅲ) complex(Ir1) with ultrasmall gold nanoparticles(AuNPs) for efficient tumor sonodynamic therapy(SDT) for the first time.AuNPs@Ir1 rapidly entered the cancer cells,produced ^(1)O_(2),and catalytically oxidized NADH to NAD;under ultrasound(US)irradiation,thus resulted in cancer cells oncosis.Because of efficient passive retention in tumors post intravenous injection,AuNPs@Ir1 further efficiently inhibited the growth of tumors in-vivo under US stimulation without long-term toxicity to other organs.Overall,this work presents the excellent US triggered in-vitro and in-vivo anticancer profile of the novel AuNPs@Ir1.It is expected to increase the scope of SDT for metal-based anticancer drugs.