TiSiC,TiSiC-Zr,and TiSiC-Cr Coatings—Corrosion Resistance and Tribological Performance in Saline Solution

TiSiC coatings alloyed with Zr and Cr were deposited on Si and 316 L steel substrates by a cathodic arc method in a CH₄ reactive atmosphere. The corrosion and wear behavior of the coatings in 0.9% NaCl solution was investigated. Corrosion resistance of the coatings was evaluated by electrochemical tests. The electrochemical polarization measurements were conducted at room temperature in the potential range ?1 and 1.5 V, with a 0.167 mVs^?1 scan rate. Compared to the uncoated 316 L substrates, the coated ones showed nobler characteristics, with more electropositive corrosion potentials, lower corrosion current densities, and higher polarization resistances. TiSiC-Zr exhibited the lowest corrosion current density (0.62 μAcm^?2) and the highest protection efficiency (69.5%). The tribological performance of the coatings under corrosive conditions (0.9% NaCl solution) was investigated using a ball-on-disc tribometer (6-mm-diameter sapphire ball, 5 N load, 0.15 ms^?1 sliding speed, 400 m sliding distance). The TiSiC-Cr coating demonstrated the best wear behavior, with a wear rate of 3.2 × 10^?6 mm³N^?1m^?1, followed by TiSiC and TiSiC-Zr. The morphologies and compositions of the worn surfaces were examined by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) in order to identify the wear mechanism. Corrosion, debris adhesion, and oxidation were found to be the dominant wear processes.     

Sorption and Preconcentration of Vanadium,Chromium, Manganese,and Lead on Silica Gel Modified with (3‐Mercaptopropyl) Trimethoxysilane

Abstract

3‐mercaptopropyltrimethoxysilane, (CH₃O)₃SiCH₂CH₂CH₂SH, loaded on silica gel was used as a preconcentration sorbent for V, Cr, Mn and Pb prior to their determination by graphite furnace atomic absorption spetrometry (GFAAS). Surface characteristics and surface area of the silica gel before and after chemical modification were determined by elemental analysis. The retention and recovery of the analyte elements were studied by applying batch and column techniques. The experimental parameters, such as the effect of pH of the sample, shaking time in batch technique, flow rate of the eluent, the concentration of acid solution in the column section, and the amount of silica on retention and elution have been investigated. All elements were quantitatively (≥90%) recovered in the batch technique with R.S.D. values of 3.0 for vanadium, 1.8 for chromium, 1.7 for manganese, and 0.4 for lead. The same recoveries were obtained in the column techniques for all elements, while manganese in sea water could not be succesfully recovered. Detection limits of the method for vanadium, chromium, manganese, and lead are 1.1, 1.4, 1.3, and 0.8 ng, respectively.     

Organic optoelectronics ： materials, devices and applications

1Introduction Beforethediscoveryofelectricallyconduc tivepropertiesthroughdoping,polymerswere widelyusedaselectricalinsulatorsduetothesu periorinsulatingpropertiestheyexhibited.In1977,thediscoveryofthefirsthighlyconductive polymer,chemicallyandelectrochemicallydoped polyacetylene,wasreported[12].Thediscovery ofdopedpolyacetylenehasopenedanentirenew fieldforpolymersandorganicmaterialsintheir applicationstobothconductorsandsemiconduc tors.Althoughtheinitialemphasiswasonthe conductivepropertiesob…     

Tribology,lubricants and lubrication engineering — a review

In this review paper more than 200 papers published between 1974 and 1976 are evaluated. These papers deal with the fundamentals of friction, wear and lubrication, including the state of friction, lubrication and materials. Another important subject is the analytical data and properties of mineral oil and synthetic lubricants, lubricating greases, additives and solid lubricants. Lubrication systems and lubricating devices as well as the lubrication of bearings, gears and internal combustion engines are also covered. Lubricants for machining processes and for metalworking are reviewed, as well as questions concerning the testing and evaluation of lubricants.     

Economic and economic-statistical designs of MEWMA control charts—a hybrid Taguchi loss, Markov chain, and genetic algorithm approach

Economic design of multivariate exponentially weighted moving average (MEWMA) control charts for monitoring the process mean vector involves determining economically the optimum values of the three control parameters: the sample size, the sampling interval between successive samples, and the control limits or the critical region of the chart. In the economic-statistical design, constraints (including the requirements of type I error probability and power) are added such that the statistical property of the chart is satisfied. In this paper, using the multivariate Taguchi loss approach, the Lorenzen–Vance (Technometrics 28:3-10, 1) cost function of implementing the control chart is extended to include intangible external costs along with the in-control average run length (ARL₀) and out-of-control average run length (ARL₁) as statistical constraints. A Markov chain model is then developed to estimate the ARLs and a genetic algorithm whose parameters are optimally obtained by design of experiments is used to solve the model and estimate the optimum values of the control chart parameters. A numerical example and a sensitivity analysis are provided to illustrate the solution procedure and to investigate the effects of cost parameters on the optimal designs. The results show that the proposed economic-statistical design of the chart has better statistical properties in comparison to the economic design while the difference between the costs is negligible.     

Adhesion,deformation and friction for self‐assembled monolayers on Au and Si surfaces

Using interfacial force microscopy (IFM), we investigated the tribological behavior of hexadecanethiol monolayers on Au and films of octadecyltrichlorosilane (ODTS), perfluorodecyltrichlorosilane (PFTS) and dodecane on Si. We observe a strong correlation between hysteresis in a compression cycle (measured via nanoindentation) and friction. Additionally, we suggest that the amount of hysteresis and friction in each film is related to its detailed molecular structure, especially the degree of molecular packing. This revised version was published online in September 2006 with corrections to the Cover Date.     

Current challenges and potential directions towards precision microscale additive manufacturing – Part II: Laser-based curing,heating, and trapping processes

This article is the second in a four-part series of articles providing an overview of the challenges and opportunities in microscale additive manufacturing (AM) processes with applications in fabrication of high precision micro/nano-products. Laser-based microscale additive manufacturing processes are discussed this article. Compared to the other AM processes, laser-based processes provide several unique advantages, especially in terms of a wide variety of processable materials and high volumetric throughputs. The processes discussed in this paper can fabricate complex microscale features with minimum resolutions ranging from hundreds of nanometers to hundreds of microns. However, there are several fundamental limits and trade-offs which hinder the scalability of these processes. The paper discusses the limits to the materials, resolution, geometry, and volumetric throughput and proposes approaches to mitigate these limits and improve the scalability of laser-based microscale AM processes.     

Advanced Tribometer for In Situ Studies of Friction, Wear, and Contact Condition—Advanced Tribometer for Friction and Wear Studies

An advanced ball-on-disk tribometer was developed for in situ studies of friction, wear, and contact condition during sliding. Kinetic friction force, contact resistance (R _c), acoustic emission (AE), ball position perpendicular () to the plane of the disk (ball and disk wear), and disk surface reflectance (disk wear) were all measured simultaneously during sliding experiments. Metal (440C steel) balls were slid against ceramic (n-doped polysilicon) wafers at light load (10g) and short test duration (2.5min). Significant changes in measured parameters were observed as sliding progressed. These changes are discussed, and when considered together provide new insights into friction and wear mechanisms not readily obtainable from more standard tribometers. The effects of disk run-out (effective surface waviness) on and R _c were also investigated. Friction and R _c were periodic with a period equal to the period of disk rotation. The behavior was complex, but generally going up a hill increased and decreased R _c, with the opposite behavior going down a hill. We established a critical link between low-frequency friction oscillations (LFFO) and the nature of the contact between sliding surfaces (R _c measurement). The geometric ratchet mechanism was ruled out as a cause of LFFO, as the surface slope was too small to explain the large friction oscillations. Coating the balls and wafers with lower friction materials resulted in negligible LFFO, which makes it unlikely that LFFO were simply a result of an oscillating normal force created by dynamic effects. LFFO likely have their origins in the complex nature of the contact between rubbing surfaces.     

Chemical Assessment of Bottled Drinking Waters by IC,GC, and ICP‐MS

Abstract

Bottled water brands, consisting of both local and imported types, collected from Doha city, Qatar, were evaluated for their suitability for human consumption. Water quality constituents that were analyzed include trihalomethanes (THM) by GC‐ECD, turbidity, TDS, total hardness, total alkalinity, pH, EC, major anions by IC, and major cations and trace metals by ICP‐MS. The data obtained were compared with the WHO and the USEPA drinking water standards. As, Se, Ba, and Cu were undetected in all water samples. The levels of potential toxic metals in the studied brands were generally low, except for three brands that had Cd and Pb which exceeded the WHO limits. Fluoride was generally present in all bottled water brands at levels less than the lower optimum level. The reported data for pH, turbidity, TDS, EC, alkalinity, hardness, major anions, and major cations were generally in compliance with the WHO and the USEPA standards, with exception of five brands, where the levels of TDS, EC, F, and NO₃ exceeded the WHO recommended limits. Also, it was found that the concentrations of NO₃ F, Fe, Cr, Zn, and Pb were higher in the local brands. The levels of Cd, Mn, Ca, Mg, EC, alkalinity, SO₄, TDS, THM, and hardness were higher in the domestic brands, when compared to the imported ones. The levels of Cl, pH, turbidity, and Na in the domestic brands were comparable to imported ones. Three THM were found in 29% of water samples with three brands having CHCl₂Br and CHCl₃ levels exceeding the WHO standards.

Comparison of the results of this study with the reported label values of both domestic and imported bottled water showed good agreement with pH and K values, but significant variation for Ca, Mg, F, NO₃, and SO₄ in the imported brands and relatively low variation in the domestic brands. The results of chemical analysis of SRM 1460, trace elements in water, were generally in good agreement with NIST certified values.     

Proposal of “Curved-Profile Wiper Turning” for efficient,stable, and smooth finishing

This paper presents an efficient, stable, and smooth turning method for curved-profile workpieces. Conventional wiper tools can achieve high efficiency, high chatter stability, and smooth surfaces at the same time only for linear-profile workpieces. A novel method is proposed, which extends the wiper tool concept to the curved-profile turning. In this method, a suitable wiper-edge radius is chosen for better smoothness, and the tool posture is controlled for higher regenerative chatter stability. Curved-profile turning experiments are conducted, and high efficiency, high chatter stability, and smooth surfaces are achieved at the same time by the proposed method.     

Reconfigurations of manufacturing systems—an empirical study on concepts, research, and applications

It is well known that the performance of a manufacturing system is susceptible to sudden changes in demand, either in terms of the quantity of products concerned or the product mix. Traditional manufacturing managers have been dealing with such situations by resorting to outsourcing of products; employing additional resources in terms of overtime, extra shifts, etc.; and adopting back logging policies using the goodwill of customers or making use of effective scheduling and inventory policies. However, in the recent times, they are also presented with the option of reconfiguring the manufacturing system (RMS), which offers a number of benefits. There are several keys enabling technologies to realize these benefits. The review of related literature helped in realizing that there are a number of alternative ways of resorting to reconfiguration. In this paper, the views and experiences of various researchers and practitioners as reported in literature are presented in an encapsulated manner bringing forth the multidimensional aspects of the subject area RMS. From various accounts reported in the international and Indian media, it is evident that the Indian manufacturing sector is performing well and is trying out various innovative practices; interestingly, many of which are related to RMS. A survey of Indian industries was carried out with the help of a survey using questionnaire as an instrument. The survey revealed various interesting facts about various RMS practices followed by the Indian manufacturing sector and the impact of reconfiguration on various performance measures of these organizations. The details of the survey and the findings of the same are also presented in this paper.     

Of mice, cats, and men: is human breast cancer a zoonosis?

Mouse mammary tumor virus (MMTV), a member of the betaretroviridae, is the most common cause of breast cancer (BC) in mice. MMTV is transmitted in mice both in the germline as endogenous proviruses and exogenously as infectious virions. Here, we review a variety of evidence accumulated for six decades that has suggested that a human homologue of MMTV may exist. The findings include recent studies from several independent laboratories that have detected sequences very closely related to MMTV in DNA isolated from human BC tumors. Other laboratories, however, have failed to detect the MMTV-related sequences in human DNA samples, and conclusive evidence for a human mammary tumor virus has been elusive. We also reviewed additional studies, suggesting that betaretroviruses are present in a much wider range of species than previously known, including rodents, felines, and primates. The observation that a subset of cats may be infected with a close homologue of MMTV may be of epidemiological significance for human BC. Cats may become infected by MMTV from mice, and in turn may transmit the virus to humans, possibly after selection for variants with an expanded host range.