John Duchowski

HYDAC Fluid Care Center, Fluid Care Center, Faculty Member

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Address: Saarbruecken, Germany

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Papers by John Duchowski

Industry Focus センサベースの状態監視

マシナリールブリケーション, 2008

Electron Spin Resonance (Esr) Spectra of Butylated Hydroxytoluene (BHT) as Evidence of Free Radical Formation in Electrostatic Discharge (Esd) Damaged Lubricating Oils

Electrostatic discharges were generated in typical ISO VG 46 cSt turbine lubricating oil by passi... more

Electron Spin Resonance (Esr) Spectra of Butylated Hydroxytoluene (BHT) as Evidence of Free Radical Formation in Electrostatic Discharge (Esd) Damaged Lubricating Oils

Tribologia : tarcie, zużycie, smarowanie, 2014

Electrostatic discharges were generated in typical ISO VG 46 cSt turbine lubricating oil by passi... more

Ion Exchange/Vacuum Dehydration Treatment: An Improved Approach for Conditioning and Reclamation of Phosphate Ester Hydraulic Fluids

Lubrication Engineering, 2001

Phosphate esters are widely used in a variety of hydraulic systems in both aerospace and industri... more Phosphate esters are widely used in a variety of hydraulic systems in both aerospace and industrial applications. In general, these fluids exhibit excellent lubricity and oxidative stability In addition, their fire retarding characteristics make them attractive for applications where the use of petroleum-based fluids would constitute a fire hazard. However, in the presence of water these luids hydrolyze and form acidie partial phosphates. Furthermore, the rate of hydrolysis in creases in acidic environment; hence the reaction is referred to as autocatolytic. This process be comes extremely difficult to reverse once the flu acidity reaches a certain point (usually a AN of) mgKOH/g). From that point on the fluid becomes increasingly difficult to stabilize with comentional treatment such as fuller's earth or activated alumina. In contrast, fluid treatment based on change and vacuum dehydration has been found highly effective in arresting the above fluid deg radation process and in restoring fluid properties to within limits acceptable by turbine OEMs and plant operators. This paper presents data collected over of period of over three years at several po plants throughout the US and Europe. These data confirm that fluid, which minally exceeded manufacturer specifications even by a wide margin was successfully stabilized through a combined treat ment of ion exchange and vacuum dehydration under normal operating conditions.

Ring tilting and the barriers to rotation of arene rings π-bonded to transition metals

Journal of the Chemical Society, 1988

Prevention of Electrostatic Charge Generation in Filtration of Low-Conductivity Oils by Surface Modification of Modern Filter Media

Tribology transactions, Jan 8, 2020

The electrostatic charging behavior of filter elements operating in various hydraulic and lubrica... more The electrostatic charging behavior of filter elements operating in various hydraulic and lubricating fluids has been reexamined from the perspective of fundamental material properties of the two materials participating in the event. In contrast to the previously proposed mechanisms that focused predominantly on fluid and material conductivities, new evidence strongly suggests that the relative placement of the substrates in the triboelectric series must be taken into account. The positions occupied in the triboelectric series account for the donor/acceptor tendencies exhibited by the materials when brought close together in close proximity (10 nm). Nevertheless, this behavior is only an outward manifestation of the deeper underlying characteristics that include material surface energies and, looking even deeper, the associated electron work functions of the interacting materials. Herein we provide several examples of the enhanced understanding of the electrostatic charging/discharging (ESC/ESD) phenomena as they occur in the course of filtration of hydraulic and lubricating fluids through modern filter elements constructed of synthetic glass fiber and polymer materials.

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Spectroscopic characterization of lanthanide octaethylporphyrin sandwich complexes. Effects of strong .pi..pi. interaction

Journal of the American Chemical Society, Apr 1, 1990

AOC. IYYU, / / I , jj I 2-33 I I(of thesc rcsults and a discussion of their interpretation are fo... more

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Effects of steric and electronic interactions on .pi..pi. overlap in lanthanide porphyrin sandwich complexes

The Journal of Physical Chemistry, Aug 1, 1990

Electrochemical, infrared, resonance Raman, and optical absorption data are reported for the lant... more Electrochemical, infrared, resonance Raman, and optical absorption data are reported for the lanthanide porphyrin sandwich complexes, Ce{sup IV}(TPP){sub 2}, Ce{sup IV}(TPP){sub 2}{sup +}, Eu{sup III}(TPP){sub 2}, Ce{sup IV}(TPnP){sub 2}, Ce{sup IV}(TPnP){sub 2}{sup +}, and Eu{sup III}(TPnP){sub 2} (TPP = meso-tetraphenylporphyrin; TPnP = meso-tetrapentylporphyrin). The two Eu{sup III} complexes contain a single hole in the porphyrin {pi} system and are electronically similar to the Ce{sup IV} sandwich porphyrin cation radicals. Variable-temperature UV-vis and near-infrared (near-IR) spectra are obtained for all four single-hole sandwiches. At high resolution and/or at low temperatures, well-resolved fine structure is observed on the intradimer charge-transfer bands (ca. 1,300 and 1,100 nm for the TPP and TPnP complexes, respectively). These absorptions are dominated by a single Franck-Condon-active vibration. This vibration is assigned as a mode, Q{sub AB}, which contains a significant amount of multicenter character and modulates inter-ring separation.

Effects of .pi..pi. interaction on the electronic properties of asymmetrical lanthanide porphyrin sandwich complexes

Inorganic Chemistry, Oct 1, 1990

knowni9 to exist in aqueous solutions in an equilibrium with LNi(H20)22+. LNi2+(aq) + 2H20 + LNi(... more knowni9 to exist in aqueous solutions in an equilibrium with LNi(H20)22+. LNi2+(aq) + 2H20 + LNi(H20)22+ (13) The octahedral complex LNi(H20),Z+ has the high-spin electronic config~ration.'~ Pressure-dependence studies of this equilibrium reaction revealed that AVI3 is considerably smaller than expected, i.e. AV13 =-1.2 f 0.1 cm3 mol-'20 or AVl3 =-3.5 f 0.1 cm3 m01-I.~' The authors assumed that these small volumes of reaction stem from a cancellation of a negative Avcoordination by a positive Avexpansion. The latter value stems from the change from low spin to high spin and was estimated to contribute 8.1 cm3 mol-' for the nickel-cyclam complex. This process clearly cannot contribute to A'VS,. The results thus seem to suggest that two axial water molecules, though not bound to the nickel, occupy the cavities formed by the ligand. These water molecules block the approach of the 'CH3 free radical to the central cation, and one of them has to be partially extricated from the cavity prior to the nickel-carbon bond formation. This process, which is speculative at this stage, explains the small positive value of AVl. We plan to extend this study to similar systems in order to check this hypothesis. Acknowledgment. We wish to thank D. Carmi, Y. Nahon, and Y. Nehemia for technical assistance. This research was supported in part by a grant from G.I.F., the German-Israeli Foundation for Scientific Research and Development, and by a grant from the Israeli Academy of Sciences and from the Planning and Granting Committee of the Council for Higher Education and the Israel Atomic Energy Commission. D.M. expresses his appreciation to Mrs. Irene Evens for her continuous interest and support. Registry No. (cyclam)(H20)Ni"'-CH3z+, 11 7687-73-7. The spin state of the complex L(H20)Ni'i'-CH,2+(aq) is not known. However, all other L(H20)Ni"'-X or LNii1'-X2 complexes, where X is a stabilizing ligand that is usually an anion, are known to have the low-spin electronic configuration.Is

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Spectroscopic characterization of triple-decker lanthanide porphyrin sandwich complexes. Effects of strong .pi..pi. interactions in extended assemblies

Journal of the American Chemical Society, Nov 1, 1990

Electrochemical, optical absorption, near-infrared, infrared, resonance Raman, and electron param... more Electrochemical, optical absorption, near-infrared, infrared, resonance Raman, and electron paramagnetic resonance data are reported for several neutral and singly oxidized triple-decker lanthanide porphyrin sandwich complexes Ln,(OEP), (Ln = La(l1l). Ce(Ill), Eu(1Il); OEP = octaethylporphyrin). The data indicate that there are strong K H interactions between the porphyrin macrocycles in all of the complexes. As a consequence, the hole in the porphyrin K system of the LII,(OEP)~+ systcms is delocalized over all three rings on the vibrational and electronic time scales. The singly oxidized complexes exhibit a charactcristic electronic absorption band at very low energies (ca. 2200 nm). This absorption arises as a direct consequence of thc strong K K interactions between the rings. A molecular orbital scheme is proposed that accounts for this low-energy feature as well as a number of other properties of the triple-decker sandwich complexes. I. Introduction Stacked and bridged porphyrinic assemblies exhibit unusual optical, redox, electron-transfer, and conductivity properties due to strong aa interactions between the macro cycle^.'-]^ We and others have been investigating the consequences of these inter

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Hole delocalization in oxidized cerium(IV) porphyrin sandwich complexes

Journal of the American Chemical Society, Aug 1, 1988

... 61 19 Hole Delocalization in Oxidized Cerium( IV) Porphyrin Sandwich Complexes Robert J. Dono... more

Optical Response of Linear Polyenes: Extension of the Simple Model for Linear Polyene Electronic Structure

Molecular crystals and liquid crystals science technology. Section A, Molecular crystals and liquid crystals (CD-ROM), Nov 1, 1994

A simple model based on Hückel theory that quantitatively accounts for linear polyene 2Ag and 1Bu... more A simple model based on Hückel theory that quantitatively accounts for linear polyene 2Ag and 1Bu excitation energies has been used to predict nonlinear optical response of this class of molecules. The essential elements of the model are the use of alternating resonance integrals to obtain the proper chain-length dependence of the 1Bu highest occupied molecular orbital (HOMO) to lowest unoccupied molecular orbital (LUMO) excitation energy and mixing of the HOMO to LUMO + 1, HOMO-1 to LUMO and HOMO to LUMO double-excitation configurations to describe the 2Ag state. Even though one of the appealing features of this model is the ease with which it can be extended to include vibrational levels, this contribution focuses on calculations carried out in a purely electronic basis. Despite the extreme simplicity of the model, it reproduces many of the results of much more elaborate computations including the fact that a higher lying Ag state has substantially larger 2-photon absorptivity than does the 2Ag state and the fact that two photon resonance with the 2Ag state can provide significant enhancement of the nonlinear optical response of these molecules at wavelengths well below the one-photon absorption edge.

Absorption and resonance Raman spectra of bis(porphyrin)europium(1+) complexes: oxidation-induced enhancement of porphyrin-porphyrin .pi..pi. interaction

The Journal of Physical Chemistry, Feb 1, 1991

Absorption and resonance Raman spectra are reported for the lanthanide porphyrin sandwich complex... more Absorption and resonance Raman spectra are reported for the lanthanide porphyrin sandwich complexes Eu{sup III}(OEP){sub 2}{sup +}, Eu{sup III}(TPnP){sub 2}{sup +}, and Eu{sup III}(TPP){sub 2}{sup +} (OEP = octaethylporphyrin, TPnP = meso-tetrapentylporphyrin and TPP = mesotetraphenylporphyrin). These cations contain two holes in the porphyrin {pi} system; consequently, they are electronically similar to solution cation dimers of the form (MOEP{sup +}){sub 2}. All three of the double-hole sandwich complexes exhibit spectral features characteristic of strong {pi}{pi} interactions. In particular, a near-infrared (near-IR)absorption band is observed at 861 nm (Eu{sup III}(OEP){sub 2}{sup +}), 867 nm (Eu{sup III}(TPnP){sub 2}{sup +}), and 1,025 nm (Eu{sup III}(TPP){sub 2}{sup +}). The energies of these near-IR bands are significantly higher than those of the corresponding single-hole complexes. The blue shift of the near-IR absorption maximum of all three double-hole sandwiches undergoes a substantial blue shift as the temperature is lowered from room temperature to 11 K.

A Novel Approach to Predictive Maintenance: A Portable, Multi-Component MEMS Sensor for On-Line Monitoring of Fluid Condition in Hydraulic and Lubricating Systems

Tribology transactions, Dec 1, 2006

On-going pressure to reduce operating costs and increasing concerns about the environment are for... more On-going pressure to reduce operating costs and increasing concerns about the environment are forcing industrial equipment operators to condition monitoring procedures and improve maintenance practices to achieve optimal fluid and component service life. Realization of these goals without compromising system performance or component life often requires that new and more sophisticated condition monitoring devices need to be used. Increasingly, these can be installed directly in-line, which eliminates delays associated with off-line analysis, decreases response time, and facilitates the decision-making process should remedial action prove necessary. This paper describes operational principles of a rugged micro-electromechanical system (MEMS) sensor that comprises four sensing elements suitable for in-line condition monitoring of hydraulic and lubricating oils. Preliminary laboratory data suggest that the sensor exhibits an excellent correlation with conventional laboratory viscosity and acid number (AN) data. Review led by Al Segall

Ion Exchange/Vacuum Dehydration Treatment of Phosphate Esters in Industrial Applications

Journal of Synthetic Lubrication, 2005

Phosphate esters are widely used in a variety of hydraulic systems in industrial applications. Th... more Phosphate esters are widely used in a variety of hydraulic systems in industrial applications. These fluids typically exhibit good lubricity and oxidative stability. The fire-retarding characteristics of phosphate esters make them attractive ve for use in applications where petroleum-basedfluids would constitute a fire hazard. However, in the presence of water, these fluids hydrolyse and form acidic partial phosphates. Because this process accelerates in an acidic environment, the reaction is referred to as autocatalytic. Moreover, fluid degradation becomes extremely difficult to reverse once acidity reaches an acid number of I mg KOH/g. From that point on, it is increasingly hard to stabilise the fluid with conventional treatment methods such as fuller's earth or activated alumina. In contrast, fluid treatment based on a combined application of ion exchange and vacuum dehydration (IX/VD) was found to be highly effective in arresting fluid degradation and restoring fluid properties to within limits acceptable for continued operation. This paper presents data collected over a period of several years at a number of power plants throughout the USA and Europe. .The data confirm that fluids that initially exceeded manufacturer specifications even by a wide margin were successfully stabilised through a combined treatment of IX/VD under normal operating conditions.

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Wear forms of heterogeneous electro-rheological fluids working in a hydraulic clutch system

Smart Materials and Structures, 2017

The paper presents experimental results concerning the wear of heterogeneous electro-rheological ... more The paper presents experimental results concerning the wear of heterogeneous electro-rheological (ER) fluids operating as working fluids in a complex clutch system consisting of a hydrodynamic clutch and a cylinder viscous clutch. The change of electric field intensity in the clutches results in change of sheer stress values in working fluids what causes the change of transmitted torque. This work shows that the most important factors affecting the wear of the ER fluid are the electric field of high intensity, the accompanying electrical breakdown, and the high temperature of the silicone oil. In addition, the water from the humid air absorbed mainly by hygroscopic particles influences a significant impact on the wear of the working fluid. Various forms of wear particles of the fluid depending on the prevailing conditions such as working mode are observed from the microscopic aspects. It is observed that the particles are flattened, rolled out or smashed into smaller fragments, partially melted, wrinkled and glued or caked. In addition, it is identified that the partial destruction of silicone oil is occurred due to the damage of the hydrocarbon chains, as evidenced by the decrease in its viscosity and the presence of the particle matter newly containing silicon.

Peer-reviewed paper

Tribology & Lubrication Technology, 2004

Particulates and water when present in paper machine bearing lubricating systems have a direct ad... more Particulates and water when present in paper machine bearing lubricating systems have a direct adverse impact on the fatigue life of the roller element bearing, the life of the lubricant and that of filter elements, the overall system performance and reliability. The detrimental effects of these contaminants were directly observed and characterized at a major Midwestern Pulp and Paper facility. In the course of routine maintenance inspections, it became apparent that certain process enhancements could be realized by improving contamination control procedures and instituting an on-going condition monitoring program. In response to concerns noted above, desiccant breathers and vaccum dehydrators were installed to reduce and maintain moisture content in paper machine lubricating oil at suitably chosen target levels. In addition, in-line water sensors and differential pressure gauges were installed to monitor water content and track filter element service life, respectively. As a result...

Procédé de traitement de surface d'un milieu filtrant

Procede de traitement de surface, notamment de finissage, d'un milieu filtrant (14) servant a... more Procede de traitement de surface, notamment de finissage, d'un milieu filtrant (14) servant a purifier au moins partiellement des fluides, ledit milieu filtrant (14) constitue d'au moins un materiau filtrant etant traite dans au moins une zone superficielle. Ce procede est caracterise en ce qu'au moins un type de particules est depose dans la zone superficielle respective sur au moins un materiau filtrant au moyen d'un procede de depot en phase gazeuse et en ce que les particules deposees permettent de predefinir au moins une propriete du milieu filtrant (14) au moins dans la zone superficielle respective.

Ion exchange/vacuum dehydration treatment : An improved approach for conditioning and reclamation of phosphate ester hydraulic fluids

Mobile dewatering system for hydraulic fluids, lubricants and petroleum based

A system (10) dewatering industrial fluid to an industrial fluid of interest comprising a chamber... more A system (10) dewatering industrial fluid to an industrial fluid of interest comprising a chamber (36) dehydration operated by gravity receiving the industrial fluid and a source of gas (72) drying positive pressure coupled to the chamber dehydrating (36), further including a pump (24) industrial fluid coupled to a common line (22) and configured to operate in order to insert and remove fluid through the system (10) further including a valve ( 30) directional pos pump at a terminal end of the common pipe (22) and a pipe (32) inlet chamber extending from the directional valve (30) to a manifold (34) within the chamber ( 36) dehydrating operated by gravity, wherein the distribution manifold (34) is configured to evenly distribute the industrial fluid across, or about, the top of the chamber (36), and further including your Beri'ah (52) outlet chamber extending from the chamber (36) and terminating in a directional valve (20) pre pump, wherein the outlet pipe (52) operates to trans...