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Focusing on hydrofluoroolefin (HFO) refrigerant, which is expected to be applied as a green refrigerant, the effect of R1234yf on the tribological characteristics was compared with hydrofluorocarbon (HFC) refrigerant R32. Tribological tests were carried out with and without a model lubricant containing triethyl phosphate as an EP additive. R1234yf showed a lower friction coefficient and better wear resistance than R32. XPS analysis of lubricated tracks revealed that metal fluoride was formed from R1234yf and R32 and higher amount of metal fluoride was observed on the track formed under R1234yf than that under R32. The frictional characteristics of R1234yf were affected by refrigerant pressure and temperature of specimen. The higher the pressure of refrigerant and the temperature of the specimen, the better the tribological characteristics were observed. In order to clarify adsorption of refrigerant on metal surface, scratching tests were carried out under refrigerant atmosphere using a mass spectrometer. Although R32 did not adsorb, R1234yf adsorbed on nascent steel surface formed by scratching. The adsorption rate of R1234yf increased linearly with scratching speed. Since propylene also adsorbed on nascent steel surface, π-electrons in R1234yf play an important role on the adsorption. It can be concluded that R1234yf adsorbs easily on nascent steel surface resulting in formation of iron fluoride which acts as a boundary lubrication layer.

Following the previous paper focusing on tribological properties of hydrofluoroolefin (HFO) refrigerant, the adsorption behavior of refrigerants on the nascent iron surface was investigated experimentally and the adsorption structure, adsorption energy and dynamic process of chemical reaction of refrigerants were analyzed by a molecular simulation. The adsorption behavior on the nascent iron surface was highly dependent on the molecular structure of the refrigerant. HFO refrigerants with an unsaturated bond exhibited high adsorption activity, and halogen species also affected the adsorption activity. HFO showed higher adsorption activity than organic ester, phosphate ester and alkyl sulfide as model compounds of refrigerator oil. In adsorption simulation by neural network potential (NNP), HFO molecules showed large negative adsorption energy. The mechanism for this stronger adsorption of HFO species, density functional theory calculation was conducted, and it showed that HFO adsorbs on iron surface by electron donation from the molecule and back-donation from iron surface. There was also a good correlation between the experimental adsorption activity and the NNP-obtained adsorption energy. MD simulation of molecule adsorbed on the nascent surface at temperature of 298 K was subsequently done using the iron fluoride has been experimentally detected on friction track by using XPS in the first report of this study. It was concluded that the adsorption and tribochemical formation of iron fluoride from HFO are supported by molecular simulation performed in this study.

The effect of molecular structure on the traction properties of polyglycol oils was investigated using a traction tester, and in-situ observation of the oil film was performed with a micro-Fourier transform infrared spectrometer under elastohydrodynamic lubrication conditions. The sample oils used were polypropylene glycol (PPG) diol, PPG triol, PPG dimethyl ether, PPG diester, PPG diamine, PPG triamine, and poly-α-olefin. The traction coefficient and oil film thickness of the sample oils were sensitive to the functional group at the terminal of the molecule. The sample oil containing polar functional group is larger in oil film thickness and traction coefficient than non-polar hydrocarbon oil, poly-α-olefin. These results suggest that the hydrogen bonding of functional groups was strengthened by high pressure in the Hertzian contact region. Moreover, the effect of water in the sample oils on the traction behavior was discussed. Water was dissolved into the sample oils from the atmosphere during the lubrication test, and it is implied that water in PPG diamine affect the traction coefficient.

In situ observation of lubricant films formed with greases was carried out at EHL conditions with a micro-FTIR. Three urea compounds were used as a thickener and 12 mass percent of the thickener was added in PAO, respectively. From the IR spectra, CH and NH stretching vibration peaks were observed from urea greases. The film thickness and the concentration of thickener were estimated from the absorbance of CH and the ratio of absorbance of NH and CH. Two-dimensional distribution of the thickness and the concentration around Hertzian contact was obtained at the resolution of 50 μm. The thickener of urea grease was concentrated on ball and disk surfaces. It was found that the concentrate on thickener at Hertzian contact region was dependent on thickener itself. Time dependence of the thickness and the concentration at Hertzian contact were obtained at the resolution of 45 s under shearing conditions. The film thickness of urea greases at Hertzian contact was greatly decreased by shearing and the film thickness and the concentration were recovered when the condition was changed to rolling. This behavior was supposed with detachment and growth of the adhered film of the thickener. Lubricating characteristics of urea greases were discussed based on the concentration of thickener at Hertzian contact.

Research interests recently increased in studying polymer-type friction modifiers (polymer FM) consisting of a polymer backbone and a functional group because of their good friction reduction capability. However, there is no clear verification of their working mechanisms. Therefore, the polymer FM behavior at the contact region must be understood to provide mechanistic information and design further-improved polymer FMs. For this purpose, in situ observation techniques have been applied to the chemical analysis of the oil film formed from a polymer FM using a micro-Fourier transform infrared spectrometer. The experimental results indicate that the polymer concentrations at the Hertzian contact drastically increased, exceeding the bulk concentration of oil. The following new friction reduction mechanism is proposed based on the clarified polymer FM concentration: the concentrated adsorption layer of the polymer FM prevents direct contact of the surface asperities.

This study investigates the effects of both, molecular structure and surface roughness, on the tribochemical decomposition of synthetic base oils under high-vacuum conditions. Nascent steel surfaces exhibit high activity to catalyze the decomposition of synthetic oil under lubricating conditions. Decomposition was performed on multiply alkylated cyclopentane (MAC) and alkyl diphenyl ether (ADE) at the nascent surface of bearing steel 52100 and was monitored by a ball-on-disk friction tester in a vacuum chamber attached to a quadrupole mass spectrometer. Although MAC decomposed, ADE did not decompose on the flat steel surface. Steel surfaces used within this experiment underwent procedural abrasion, providing the requisite roughness to generate the nascent steel surface for the friction test. Decomposition of ADE and desorption of benzene were observed in the presence of the nascent steel surface under friction. As the surface morphology of the pretreated roughened surfaces changed during friction, the contact pressure and plasticity of the surface decreased. We concluded that the tribochemical decomposition of ADE was accelerated on rough steel surfaces by the generation of a nascent surface at the point of metal-metal contact. From these results, the critical role of a nascent steel surface on the tribochemical decomposition of syntheticoils is discussed.

The temperature dependence of friction coefficient of lubricant oils containing MoDTC was evaluated using a ball on disk tribometer at constant temperatures of 25, 40, 60 and 80°C. In the experiments, the friction coefficient gradually decreased and tended to become lower at steady state. The decreasing slope of the friction coefficient was steeper and the lower friction coefficient at the steady state was obtained at a higher oil temperature. The friction coefficient was also controlled by the concentration of MoDTC in oil. Considering that the results of lubricating tests supported the successive processes involving production and wear of MoS2, the friction coefficient can be controlled by the coverage of MoS2 which is determined by a balance of formation and wear of MoS2. An analysis formula was established based on kinetic assessment of the process in order to obtain the Arrhenius plots of the test results. There were two regions which had different slopes in the plot. The activation energies were 70 and 4 kJ/mol for the low and the high temperature regions, respectively. This result suggested that MoS2 production from MoDTC was reaction rate-limiting at low temperature and transport ratelimiting at high temperature.

In situ observation of lubricant films formed with greases was performed with a micro Fourier transform infrared spectrometer (FT-IR) under elastohydrodynamic lubrication (EHL) conditions between a steel ball and a single-crystal silicon disk. Twelve mass percent of lithium stearate or aromatic-type urea compound were added as thickener to polyalphaolefin base oil. Peaks relating to CH, C=O and NH were monitored in the FT-IR analysis. The film thickness and the concentration of thickener were estimated from the absorbance of CH and the ratio of absorbance of C=O and CH. Two-dimensional distribution of the thickness and the concentration around EHL contact was obtained at a resolution of 50 μm. It was found that the concentration of thickener at EHL contact area was dependent on the type of thickener. Although the concentration of Li grease decreased at the EHL contact area, that of urea increased even at low entrainment speed. The thickener of urea grease was concentrated on the ball and the disk surfaces. The film thickness at EHL contact of each grease can be explained by the concentration of thickener at the contact. Lubricating characteristics of urea grease are discussed based on the concentration of thickener at the EHL contact.

The effect of temperature on the lubricity of molybdenum dithiocarbamate (MoDTC) was investigated by a ball on disk tribometer with lubricant oil containing MoDTC and calcium sulfonate (CaSU) at temperatures of 25˚C, 40˚C, 60˚C and 80˚C. The behavior of friction coefficient was closely dependent on the oil temperature. Friction coefficient decreased after a certain induction period and became to be constant at steady state. At higher temperature, the induction period became to be shorter, and the slope of decreasing friction coefficient became to be steeper. Friction coefficient at steady state decreased at higher temperature, and was changed reversibly when the oil temperature was changed. Oscillatory change in friction was observed when the oil temperature was changed periodically. Chemical analysis of the tribofilm with X-ray Photoelectron Spectroscopy (XPS) revealed that higher content of Mo(IV) as a component of molybdenum disulfide (MoS2) was observed in the tribofilm formed at higher temperature. Highly oriented MoS2 layer was observed with High Resolution Transmission Electron Microscopy (HR-TEM) in the tribofilm formed at 80˚C. It was found that the structure of tribofilm is altered reversibly with oil temperature. A steady state model of tribofilm formation was proposed on the basis of observed results.

The performance of household chores by children in Japanese residential care institutions has been widely accepted as a practice that fosters children’s independence and self-sufficiency. However, children coming from neglectful or dysfunctional families often require sensitive, individualized care, which they did not receive from their family of origin. While a shift away from large-scale institutions has begun, with smaller units or group homes now accounting for 40% of all care institutions, it is not clear that family-like, individualized care has been achieved in these smaller group homes. This study involved 61 participants aged 10 to 15 years and their care workers from six residential care institutions in the greater Tokyo area. It explored what aspects of care quality were related to the presence of certain characteristics of traditional management-oriented care: fixed rules for household chores and lack of choice in daily living. Care workers were asked whether children washed their own dishes, did their own laundry, chose their own clothes when shopping, and had mandatory events to attend in the residential care institutions. Care quality was assessed using the Early Adolescent HOME (Home Observation for Measurement of Environment) developed for Japanese residential care institutions (EA-HOME-JP). The findings suggest that care workers should re-examine their intentions in setting and applying household chore rules while exploring which aspects of child care, including regulatory activities and modeling, should be emphasized in order to actualize family-like and individualized care in institutions.

The performance of wire drawing is closely dependent on lubrication between die and metal wire. The behavior of lubricants between the die and the wire plays an important role in the lubricating performance for wire drawing. Therefore, the lubricant behavior should be made clearer by a direct observation of the drawing interface in die. The objective of this work is to understand the behavior of lubricants based on the chemical reactions for wire drawing. The drawing properties of these lubricants are discussed on the basis of the generation of metal soap. In situ observation of lubricant film during wire drawing was carried out using a micro-Fourier transform infrared spectroscopy (FTIR). The infrared (IR) spectra of oil film between die and metal wire can be obtained and oil film shape and concentration of additive can be estimated. It was found that oleic acid as an additive reacts with metal wire chemically and metal soap was formed. The concentration of metal soap was distributed to be high at the end of reduction zone under the dynamic conditions.

In order to foster interactive discussions with other countries, this paper offers an overview of residential care for children in Japan and its ongoing development. Japan still relies especially heavily on the residential care system; this is due to the past process of development more than to traditional Japanese culture. The period from the post World War II era to the present is briefly described, including the rapid growth in the number of institutions before 1960, the rather stable period before 1990, the revision of the Child Welfare Act in 1997 permitting the privatization of institutions, and the movement towards problematizing child abuse in the mid 1990s, after which residential institutions were designated as the last resort for maltreated young people. In the present situation, smaller institutions and a foster care system are strongly promoted in accordance with international guidelines for alternative care and the recent governmental guideline based on the Child Rearing Vision of 2010 and the Child Welfare Act of 2016. The task of present Japanese residential care institutions is to realize a family-like environment and a better placement strategy, collaborate more with specialists to improve the standard of care, function in the community as centers for the care of children in need, and expand their care work for young adults and care leavers. The paper concludes by stressing the need for more international exchange among individuals and groups working in Japanese residential care.

The effect of temperature on the adsorption of benzene on the nascent surface of steel was examined. Cutting tests were carried out under high vacuum condition. The components adsorbed onto or desorbed from the nascent surfaces formed by cutting were monitored by a quadrupole mass spectrometer. The adsorption rate of benzene decreased with increasing temperature whereas desorption rate of hydrogen and adsorption rate of water increased. It appeared that water from residual gas preferentially adsorbed onto the nascent surface to disturb benzene adsorption as the temperature increased where the water was decomposed to form hydrogen. In this study, it was found that the reaction of adsorption on mechanically formed nascent surfaces is affected by temperature. Adsorption activity of mechanically formed nascent surfaces was calculated.

Thermoreversible gel lubricant (TR gel lube) has been developed as a unique new lubricant. TR gel lube contains a high percentage of aliphatic amide as a gel agent in the base fluid. It is able to repeatedly change from a gel state to a liquid state at the melting point. Therefore, the new lubricant is expected to be useful as an impregnant for porous tribomaterial. In previous research, the lubricants exhibited good lubricity and low friction properties. These tribological properties were depended on the molecular structure and content of amide gel agents. In this study, physicochemical properties of the TR gel lube were examined to discuss in detail the lubrication mechanism. It was revealed that TR gel lube indicated a soft gel compared with general grease by measuring dynamic viscoelasticity. Entropy changes of TR gel lubes were depended on the amide molecular structure by analyzing the thermo dynamical data. Lubricating mechanisms by oiliness effect of adsorbed gel agent and introducing to contact area were proposed.

The tribological properties of poly(ether-ether-ketone) (PEEK) against steel was evaluated by a ring-on-flat type tribo-test under rotating motion. Addition of poly(tetrafluoroethlene) (PTFE) as solid lubricants improved the load-carrying capacity of the material. The role of PTFE was studied by means of time of flight secondary ion mass spectroscopy (TOF-SIMS). The transfer of PTFE from the PEEK surface onto steel surface was found to be beneficial for preventing seizure.

Effect of di-tert-dodecyl disulfide as an additive on decomposition of MAC oil on the nascent surface of bearing steel 52100 was investigated. After the removal of surface contamination layer, active sites were generated, on which tribochemical decomposition of MAC oil occurred. The additive prolonged the induction period of the decomposition. Hydrogen and gaseous hydrocarbons desorbed as tribochemical reaction products. Desorption rate of hydrogen and gaseous hydrocarbons increased proportionally with sliding velocity and linearly with the cube root of load. XPS analysis revealed tribochemical reaction between additive and nascent surface occurred, which induced formation of iron sulfide and decrease of activity of nascent surface. As a result, decomposition of MAC oil decreased correspondingly.

Under conditions of boundary lubrication, there is direct contact and surface films such as metal oxides and organic contaminants are mechanically removed by mechanical contacts. This causes to form a chemically active nascent surface. It is essential to understand the reaction between lubricant additives and the nascent metal surface. In this research, the well known organic sulfides were selected as the model compounds of extreme pressure additives (EP additives). The catalytic effect of a nascent metal surface without thermal effect was studied using cutting method with a ceramic tip and the reaction was monitored with a quadrupole mass spectrometer. The main result is that the type of alkyl group and the number of sulfur atoms in the central chain (for instance, mono-sulfide or disulfide) have a strong influence on the adsorption and reaction of the sulfide compounds.

A new tribo-tester was developed by modification of the “Falex Pin & Vee-block” type tribo-test (ASTM D 3233). The advantages of the present method are (1) specimen made of various materials is easily available and (2) the specimen is ready to surface analysis without any processing after the tribo-test. Utilities of the new tribo-test were demonstrated by comparing additive-material compatibility. The tribological properties of aluminum/aluminum contact were improved by phosphorus containing additives, whereas those of copper/copper contact were improved by sulfur containing additives. These results were well explained by tribo-chemistry based on the results of XPS analysis.

We examined the pull-off and friction forces between an atomic force microscope (AFM) probe and submicron-scale asperities covered with Langmuir Blodgett (LB) films. First, we used a focused ion beam to produce several kinds of asperity arrays on two silicon substrates. The average radius of curvature was 95 to 800 nm, depending on the asperity array. An LB film of stearic acid (C17H35COOH) or fluoro-carboxylic acid (C6F13C11H22COOH) was deposited on each substrate. The friction force was measured at each asperity array under a zero applied load. The pull-off force was measured at each asperity array and also at controlled relative humidities of 3 to 73%. The results showed that the pull-off and friction forces were almost proportional to the radius of the curvature of the asperity peak with both stearic acid and fluoro-carboxylic acid LB films. The gradient of the friction force against the pull-off force, which corresponded to the friction coefficient, was 0.021 and 0.14 for the stearic acid and fluoro-carboxylic acid respectively. The pull-off force increased with higher relative humidity on the fluoro-carboxylic acid. We concluded that differences in the pull-off and friction forces between the two kinds of LB films were mainly caused by differences in the stiffness of the LB film.

Lubricant additive technology to improve lubricant performances is an important issue for ionic liquids to be applied practically. Effects of carboxylic acids with different carbon chain length in ionic liquid on tribological properties were examined. Solubility of carboxylic acids was dependent on the chain length of carboxylic acids and imidazolium cations. The carboxylic acids reduced friction and wear in comparison with additive free one. It was found that friction reducing properties of carboxylic acid depended on their chain length. Interestingly, additive response of ionic liquids was found to be superior to those for conventional ester oil as base oil. Surface images obtained by an optical microscope clearly show that the additive depressed chemical wear by ionic liquids especially at low load. Surface analysis with EPMA supported films of carboxylic acids as a cause of improvement of friction property. Therefore, the mechanism of carboxylic acids was considered to provide adsorbed film which accompanied with low friction and anti-wear properties.