Mechanochemical Phenomena Research Articles

High-pressure mechanochemistry: Conceptual multiscale theory and interpretation of experiments

Fifteen mechanochemical phenomena observed under compression and plastic shear of materials in a rotational diamond anvil cell (RDAC) are systematized. They are related to strain-induced structural changes (SCs) under high pressure, including phase transformations (PTs) and chemical reactions. A simple, three-scale continuum thermodynamic theory and closed-form solutions are developed which explain these phenomena. At the nanoscale, a model for strain-induced nucleation at the tip of a dislocation pile-up is suggested and studied. At the microscale, a simple strain-controlled kinetic equation for the strain-induced SCs is thermodynamically derived. A macroscale model for plastic flow and strain-induced SCs in RDAC is developed. These models explain why and how the superposition of plastic shear on high pressure leads to (a) a significant (by a factor of 3--5) reduction of the SC pressure, (b) reduction (up to zero) of pressure hysteresis, (c) the appearance of new phases, especially strong phases, which were not obtained without shear, (d) strain-controlled (rather than time-controlled) kinetics, or (e) the acceleration of kinetics without changes in the PT pressure. Also, an explanation was obtained as to why a nonreacting matrix with a yield stress higher (lower) than that for reagents significantly accelerates (slows down) the reactions. Some methods of characterization and controlling the SCs are suggested and the unique potential of plastic straining to produce high-strength metastable phases is predicted.

Strain-induced nucleation at a dislocation pile-up: a nanoscale model for high pressure mechanochemistry

A simple continuum thermodynamic model of strain-induced nucleation at the tip of a dislocation pile-up is developed. This model is applied to explain various mechanochemical phenomena. In particular, it explains why and how the superposition of plastic shear on high pressure leads to: a significant (by a factor of 3–5) reduction of phase transition's and chemical reaction's pressure and pressure hysteresis, the appearance of new phases which were not obtained without shear, strain-controlled (rather than time-controlled) kinetics, or the acceleration of kinetics without changes in the transformation pressure.

Surface plasticity modification using electrolytic etching

Any surface treatment of a solid changes its chemical reactivity and mechanical properties, at least within a thin surface layer. Some practical applications to metal surface treatment based on quantitative analysis of the mechanochemical phenomena are presented. One of the results of mechanochemical surface treatment is the possibility to decrease the residual stresses and the hardness of the surface layers, as a result of the chemomechanical effect, and also to produce a passive surface protective film that increases the adhesion of the coating and improves the corrosion resistance. In addition, it is possible to improve the deep drawing ability for high strength alloys.

Thermal decomposition kinetics of ammonium uranyl carbonate

The thermal decomposition kinetics of AUC [ammonium uranyl carbonate; (NH 4) 4UO 2(CO 3) 3] in an isothermal thermogravimetric (TG) reactor under N 2 atmosphere has been determined. The kinetic data can be represented by the two-dimensional nucleation and growth model. The reaction rate increases and activation energy decreases with increasing particle size and precipitation time which appears in the particle size larger than 30 μm in the mechano-chemical phenomena.

Mechanochemical phenomena of gibbsite, bayerite and boehmite by grinding

Three hydrated aluminas, gibbsite, bayerite and boehmite, were ground in air for 0.25–20 h by a planetary ball mill. The effect of grinding on their texture, structure and thermal behaviors has been examined by means of XRD, TG, DTA, SEM, IR, particle size distribution and nitrogen gas adsorption. It was found that in the initial stages of grinding (within the first 1 h), the specific surface area, S, had increased in the gibbsite, decreased in the bayerite and had a maximum in boehmite, and then proceeded to achieve their respective equilibrium values. These behaviors were correlated with changes in the median size, d 50, as a measure of the aggregate size of the particles. Prolonged grinding times, led to a decrease in the intensity of X-ray diffraction lines and an increase in the half-maximum line breadth. After 4 or 8 h grinding all the hydrated aluminas had been changed to the amorphous phase without mechanochemical dehydration. Moreover, the DTA endotherms attributable to the dehydration of the hydrated aluminas gradually diminished on grinding, and a set of broad endotherms appeared at about 150 or 200 °C for the amorphous phases. Whereas the transformation sequences of the unground hydrated aluminas to α-Al 2O 3 showed gibbsite → χ → κ → α, bayerite → η → θ → α and boehmite → γ → δ → θ → α, all the amorphous phases showed the amorphous hydrated alumina → amorphous alumina → η → α and the temperature of α-transformation had been lowered by more than 200°C.

微粉砕に伴う固体材料の化学変化 Ｉ メカノケミカル現象の特色と理論

微粉砕に伴う固体材料の化学変化 Ｉ メカノケミカル現象の特色と理論

微粉砕に伴う固体材料の化学変化 ＩＩ メカノケミカル現象の実験的手法と応用

微粉砕に伴う固体材料の化学変化 ＩＩ メカノケミカル現象の実験的手法と応用

Mechanochemical phenomena in thermoplastic polyurethane film during fatigue tests

Mechanochemical phenomena in thermoplastic polyurethane film during fatigue tests

IR spectroscopic study of mechanochemical processes in polymers stimulated by orientation stretching

Using IR spectroscopy and bromination it is shown that on orientation stretching of PP and PVC fibres new chemical groupings form: C C bonds, hydroxyl and carbonyl groups, pointing to free-radical chain reactions. The results indicate the need to allow for mechanochemical phenomena on formation and orientation stretching of fibres and films.

摩砕による金属硫化物およびセレン化物のメカノケミカル変化

摩砕による金属硫化物およびセレン化物 : HgS, HgSe, ZnS, CdS, CdSeのメカノケミカル変化について検討した。これら化合物の結晶型は, 閃亜鉛鉱型とウルツ鉱型との2種類が知られている。摩砕による混合物のメカノケミカル現象は, 色彩およびX線回折図の変化から比較した。X線回折によると・HgS (cub.) は摩砕により容易にウルツ鉱型に転移したが, HgS (hex.) は閃亜鉛鉱型に転移しなかった。HgS (cub.) -ZnS (cub.), CdS (cub.) -ZnS (cub.) およびCdS (hex.) -CdSe (hex.) の各二成分系の混合物は, 摩砕により閃亜鉛鉱型の連続置換固溶体に変化し, その格子定数はVegardの法則にのり直線的に変換した。一方, HgS (cub.) -HgSe (cub.) およびCdS (hex.) -HgS (hex.) 系二成分の混合物の場合も摩砕により固溶体に変化したが, その結晶型は二成分の混合比によって変わることを認めた。CdS (hex.) /HgS (hex.) =8/1混合物の摩砕からできた閃亜鉛鉱型固溶体の色相は黄みの赤色 (主波長600.7nm) を示し, そのX線回折線はCdS (cub.) のそれと一致した。

摩砕によるリン酸三コバルト八水和物のメカノケミカル変

摩砕によるリン酸三コバルト八水和物のメカノケミカル変

Polymer expands 35% upon uv irradiation

When a collection of long polymeric molecules experiences a change of chemical environment, the system may under certain circumstances exhibit a contraction or dilation, sometimes generating considerable mechanical forces in the process. Such “mechanochemical” forces have in fact been put to work in an isothermal chemical engine invented by Aharon Katchalsky‐Katzir and his colleagues at the Weizmann Institute in 1966. The original impetus for the study of mechanochemical phenomena in the early 1950's was an attempt to understand the mechanisms of muscle contraction.

Effect of the surface activity of polymers during degradation on the friction and wear of plastic-metal and metal-metal pairs

The results of studies on the reasons why degradation products of polymers migrate into the metal and the metal is transferred into the plastic material during friction are discussed. Saturation of the steel surfaces with the degradation products of the polymers has been shown in the case of electropositive plastic counterbody, and decarbonization of steel surfaces in the case of the electronegative polymeric counterbody; a hypothesis has been put forward on the triboelectric and mechanochemical phenomena for the friction and wear processes of the plastic-metal and metal-metal pairs.

Effect of deformation on electrochemical properties of the double layer and surface charge of metals

Electrochemical measurements on plastically deformed metals revealed the previously predicted [1] deformation-induced shifts toward positive surface charge values and clarified the character of the intensification of the electrochemical heterogeneity of deformed metal surfaces (localization of activated anodes as a result of mechanochemical phenomena). The deformation-induced increase in the differential capacitance of the double layer is attributable to an increase in the intensity of physical (electrostatic) adsorption of SO 4 2− and HSO 4 − HSO 4 − anions on a positively charged surface in sulfuric acid solutions. A necessary (but not always sufficient) condition of the effectiveness of cation-active inhibitors of corrosion of plastically deformed metals is their stable chemisorption at potentials in the range of deformation-induced changes in the surface charge (of the order of tenths of a volt on the ϕ-scale).

粉砕操作に涛けるメカノヶミストリー

粉砕操作に涛けるメカノヶミストリー

Mechanochemical Phenomena Structure and Functions of Contractile Proteins Boris F. Poglazov

Mechanochemical Phenomena Structure and Functions of Contractile Proteins Boris F. Poglazov

Mechanochemical Effects in Fatigue of Rubber

Abstract 1. It has been shown that the effectiveness of the action of antifatigue agents changes depending on the method of addition to the rubber. 2. The change in effectiveness of such agents points to the fact that there is significant connection between mechanochemical phenomena occurring during milling and fatigue of the polymer, which must be taken into account in manufacturing practice. 3. The effect of preliminary milling of the rubber with antifatigue agents on fatigue life of the compound apparently can be explained as resulting from consumption of antifatigue agents in the milling process, owing to mechanochemical reactions.

Mechanochemical Phenomena in Polymers. II. The Effects of Initiators and Inhibitors of Chain Processes

Abstract 1. The substantial effect of inhibitors and initiators of chain radical processes on the change in the properties of rubbers in milling, as well as on the resistance of vulcanizates to fatigue, has been shown. This indicates a mechanochemical mechanism for processing of polymers and in the fatigue of elastomers. The act of mechanical scission of chemical bonds, with the formation of free radicals which initiate the secondary chain processes, rests on these processes. 2. The possibility has been shown of regulating the properties of polymers during processing, and also of increasing the dynamic fatigue resistance of vulcanizates by incorporating small quantities of additives active in regard to free radicals.

Mechanochemical Phenomena. I. Chemical Flow in Raw and Vulcanized Rubber

Abstract 1. The authors demonstrate the essential role of mechanochemical phenomena in processing. Attention is paid to the necessity of taking into account the phenomenon of chemical flow. 2. From the example of various vulcanizates there is demonstrated the possibility of mechanical processing of crosslinked polymers. Attention is paid to the significance of mechanochemical phenomena in reclaiming. 3. A demonstration is given of the influence of small additions of substances which form free radicals or which interact with them, upon the kinetics of the alteration of the properties of a polymer on prolonged milling. Attention is paid to the possibility of controlling the properties of a polymer during processing. 4. The authors show the necessity of taking into account the phenomenon of chemical flow in developing objective methods of laboratory assessment of the technological properties of polymers.

Mechanochemical phenomena in polymers—V. Effect of the processing of the rubber hydrocarbon on the fatigue of rubbers : G. I. Slonimskii and Ye. V. Reztsova, Vysokomol. soyed. 4: No. 10, 1571–1574, 1962

Mechanochemical phenomena in polymers—V. Effect of the processing of the rubber hydrocarbon on the fatigue of rubbers : G. I. Slonimskii and Ye. V. Reztsova, Vysokomol. soyed. 4: No. 10, 1571–1574, 1962