In this study, the surface of steel tooth drill bits (Ni-Cr-Mo based) was subjected to the solidstate boriding treatment with 10-50 nm particle size Nanoboron powder. Boriding processes was carried out at a constant temperature of 1273 K for 30, 45, 60, 75, 90 and 105 minutes using a solid-state box boriding technique. Borided drill bit samples were characterized by conventional methods (microstructure, microhardness, X-ray diffraction and chemical analysis). Wear behaviour of borided samples was tested at different loads and sliding speeds by a microabrasion experimental set up. Metallographic studies showed that the boride layers have a sawtooth morphology and consist of FeB and Fe 2 B. The thickness and hardness of the boride layer was found to be 35.29 -202.56 μm and, 1300-2333 HV 0.1 , respectively, depending on the duration time. The wear resistance of borided samples increased significantly due to the increase in surface hardness and lubricating effect both of which were caused by boriding process.Grooving wear mechanism prevailed in borided samples, while that of bare steel tooth drill bits (STDB) was grooving, rolling and mixed. INTRODUCTIONDrilling is the operation of opening holes in the earth's surface with the help of a drill bit.Drilling systems are divided in two ones as rotary and percussion. Although the rotary system is preferred in deep drilling, both systems have their advantages and disadvantages. In both systems, the drilling performance usually determines the cost of drilling. The drilling performance depends on the drill bit selection as well as the use of the drill bit. Significant cost reductions are ensured through choosing a reliable drill bit (Moore (1); Grimes, et. al. (2); Bobo(3)).The rotational speed of the drill is as effective as the drill selection on the drilling costs and service life of the drill bits. Rotation speed is recommended as 30-40 rev/min in lower surface drillability, 60-120 rev/min with the ability to drill in surface and 70-140 rev/min in the surface of higher ability to drill. In very soft rock rotation speed can be 200-250 rev/min (Moore (1); Cummins (4)).To increase the drilling rate, compression force should be kept constant and the rotational speed must be increased. However, increasing the rotational speed results in an increase in the temperature of the drill bit surface and it accelerates the corrosion and wear (Moore (1); Praillet (5)). Modifications on these materials should be made to ensure the resistance of the drill bit to high temperature conditions.In the improvement of the mechanical characteristics of the steel materials, the most convenient and economical way is surface hardening. Surface hardening methods provide Downloaded by [University of Leeds] at 14:07 05 June 2016 ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT 4material surfaces with harder, strong, and abrasion-resistant structures; and a more energyabsorbent inner structure which provides toughness (Ulutan, et. al. (6)). Boriding heat treatment is a commonly used hardening process (ġen, et. ...
, "Coagulation measurement from whole blood using vibrating optical fiber in a disposable cartridge," J. Biomed. Opt. 22(11), 117001 (2017), doi: 10.1117/1.JBO.22.11.117001. Abstract. In clinics, blood coagulation time measurements are performed using mechanical measurements with blood plasma. Such measurements are challenging to do in a lab-on-a-chip (LoC) system using a small volume of whole blood. Existing LoC systems use indirect measurement principles employing optical or electrochemical methods. We developed an LoC system using mechanical measurements with a small volume of whole blood without requiring sample preparation. The measurement is performed in a microfluidic channel where two fibers are placed inline with a small gap in between. The first fiber operates near its mechanical resonance using remote magnetic actuation and immersed in the sample. The second fiber is a pick-up fiber acting as an optical sensor. The microfluidic channel is engineered innovatively such that the blood does not block the gap between the vibrating fiber and the pick-up fiber, resulting in high signal-to-noise ratio optical output. The control plasma test results matched well with the plasma manufacturer's datasheet. Activated-partial-thromboplastin-time tests were successfully performed also with human whole blood samples, and the method is proven to be effective. Simplicity of the cartridge design and cost of readily available materials enable a low-cost point-of-care device for blood coagulation measurements.
We developed two types of cantilever-based biosensors for portable diagnostics applications. One sensor is based on MEMS cantilever chip mounted in a microfluidic channel and the other sensor is based on a movable optical fiber placed across a microfluidic channel. Both types of sensors were aimed at direct mechanical measurement of coagulation time in a disposable cartridge using plasma or whole blood samples. There are several similarities and also some important differences between the MEMS based and the optical fiber based solutions. The aim of this paper is to provide a comparison between the two solutions and the results. For both types of sensors, actuation of the cantilever or the moving fiber is achieved using an electro coil and the readout is optical. Since both the actuation and sensing are remote, no electrical connections are required for the cartridge. Therefore it is possible to build low cost disposable cartridges. The reader unit for the cartridge contains light sources, photodetectors, the electro coil, a heater, analog electronics, and a microprocessor. The reader unit has different optical interfaces for the cartridges that have MEMS cantilevers and moving fibers. MEMS based platform has better sensitivity but optomechanical alignment is a challenge and measurements with whole blood were not possible due to high scattering of light by the red blood cells. Fiber sensor based platform has relaxed optomechanical tolerances, ease of manufacturing, and it allows measurements in whole blood. Both sensors were tested using control plasma samples for activated-Partial-Thromboplastin-Time (aPTT) measurements. Control plasma test results matched with the manufacturer's datasheet. Optical fiber based system was tested for aPTT tests with human whole blood samples and the proposed platform provided repeatable test results making the system method of choice for portable diagnostics.
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