Yuko Aono

Measurement of Crystallization Temperature Using Thermography for Thin Film Amorphous Alloy Samples

This report describes a new non-contact measurement method for the crystallization temperature (Tx) of a thin film amorphous alloy. The thermal emissivity of the amorphous alloy sample is predicted to be modified when it crystallizes. It was attempted to relate this modification to changes in the apparent temperature by thermography. Thin film amorphous alloys of Pt67Si33 and Pt73Si27 were sputtered onto an Al2O3 substrate and then heated at 20 K/min in vacuum, and the film temperature was monitored by thermography. The Tx indicated by the proposed method coincided with the temperature measured by conventional differential scanning calorimeter within 8 K.

Reduction in static friction by deposition of a homogeneous diamond-like carbon (DLC) coating on orthodontic brackets

In orthodontics, a reduction in static friction between the brackets and wire is important to enable easy tooth movement. The aim of this study was to examine the effects of a homogeneous diamond-like carbon (DLC) coating on the whole surfaces of slots in stainless steel orthodontic brackets on reducing the static friction between the brackets and the wire. The DLC coating was characterized using Raman spectroscopy, surface roughness and contact angle measurements, and SEM observations. Rectangular stainless steel and titanium-molybdenum alloy wires with two different sizes were employed, and the static friction between the brackets and wire was measured under dry and wet conditions. The DLC coating had a thickness of approximately 1.0 μm and an amorphous structure was identified. The results indicated that the DLC coating always led to a reduction in static friction.

Evaluation of the Validity of Crystallization Temperature Measurements Using Thermography with Different Sample Configurations

We describe further progress of a previously reported novel crystallization temperature (Tx) measurement method applicable for small sample sizes. The method uses thermography and detects Tx as a change in emissivity of thin film amorphous alloy samples. We applied this method to various sample configurations of Pd–Cu–Si thin film metallic glass (TFMG). The validity of the detected Tx was determined by electrical resistivity monitoring and differential scanning calorimetry (DSC). Crystallization temperature can be detected in all sample configurations; however, it was found that the magnitude of the detected change of emissivity at Tx depended on the sample configuration. This emissivity change was clear in the absence of a higher emissivity material. The results suggest that this method can achieve high-throughput characterization of Tx for integrated small samples such as in a thin film library.

High-Throughput Characterization Method for Crystallization Temperature of Integrated Thin Film Amorphous Alloys Using Thermography

We introduce the high-throughput characterization of the crystallization temperature Tx of thin film amorphous alloys integrated into a thin film library. This characterization is achieved using thermography. A new thin film library is designed and fabricated using photolithography and a lift-off process. Using a homogeneous composition thin film library, the validity of the proposed method is confirmed. The crystallization of all samples can be detected simultaneously, and the measured Tx distribution is about 8 K. Three compositionally distributed thin film libraries of the Pd–Cu–Si alloy system were then fabricated using combinatorial arc plasma deposition (CAPD), and the Tx values of the samples on the three libraries were measured. In the three libraries, Tx for 285 amorphous samples could be measured, and there was an obvious distribution in Tx depending on the sample composition. At two selected compositions, the measured Tx values agree with differential scanning calorimetry (DSC) results within 8 K. In terms of throughput, the proposed method achieves a measurement time reduction of 66% compared with a conventional method using DSC. Consequently, the proposed method enables the high-throughput combinatorial characterization of the Tx of thin film amorphous alloys.

High-Throughput Measurement Method for Time--Temperature-Transformation Diagram of Thin Film Amorphous Alloys

The time–temperature-transformation (TTT) diagram of amorphous alloys is important for the applications of alloys. However, measurement for it by the conventional method is a time-consuming process. We propose a high-throughput measurement method for compiling TTT diagrams of thin film amorphous alloys. For this method, a temperature gradient furnace system is used. The thin film sample is isothermally heated with a temperature gradient and monitored by thermography. Thermography can detect crystallization. Therefore, the times required for crystallization at various temperatures can be measured at once. The validity of this method is shown by comparison with the results of the conventional method.

High-Throughput Evaluation of Crystallization Temperature of Pd-Cu-Si System Using Integrated Thin Film Samples

In this paper, a new high-throughput evaluation method for crystallization temperature (Tx) of thin film amorphous alloy is introduced. For measurement of Tx on integrated thin film samples, thermography is used. The order of one hundred Pd-Cu-Si thin film amorphous samples with different composition are integrated on one chip and measured their Tx at once. The validity of measured Tx are examined by comparing with results of differential scanning calorimeter that is a conventional method for Tx measurement, and equilibrium phase diagram of Pd-Si. As results, the difference of two methods is within 10 K and the trend of Tx map has strong correlation with the phase diagram, respectively.

Local Wettability Modification and its Micro-Fluidic System Application

Micro-fluidic systems function as promising devices in many fields such as biochemistry and conventionally consist of packaged groove-type micro-channels. In this chapter, surface flow channels independent of geometric formation such as grooves are introduced. The surface flow channels are based on wettability modulation. Liquid preferentially flows toward more wettable surface; Y. Aono · A. Hirata (*) Department of Mechanical Engineering, Tokyo Institute of Technology, Tokyo, Japan e-mail: aono.y.aa@m.titech.ac.jp; hirata.a.aa@m.titech.ac.jp # Springer Nature Singapore Pte Ltd. 2018 J. Yan (ed.), Micro and Nano Fabrication Technology, Micro/Nano Technologies, https://doi.org/10.1007/978-981-10-6588-0_30-2 1 therefore a locally modified surface with higher wettability can function as a surface flow channel even if the modified surface is entirely flat and an invisible line. Furthermore, a surface channel with gradient of wettability demonstrates self-transportation ability for micro-droplets. This chapter especially focuses on the local modifications and modulations of wettability on silicon and glass substrates using laser irradiation, which change surface chemical composition or nanoscale roughness by laser thermal effect. The laser modification results in wide range of contact angles from 40 to 110 on silica glass of which surface is pretreated with hydrophobic terminal groups (-CF3). The variation of wettability is caused by thermal decomposition of the terminal groups depending on laser irradiation conditions. The correlation between the remaining surface hydrophobic group and contact angle is confirmed by quantitative analysis of fluorine on the surface. In addition, this chemical modification preserves surface geometry and transparency of the substrate. The local wettability modification by laser irradiation is then applied to form micro-fluidic systems and achieves invisible surface flow channel with self-transportation ability by spatial wettability control.

Novel combinatorial method for evaluation of machinability for glass lens mold material

Recently, miniaturization of optical components becomes one of the most attractive subjects in the optics industry, by combining multiple optical functions into single optical components with microstructures. The mold to produce those optical components is required to be able to be machined to desired microstructures with high precision on the surface. Since the existing machining methods are either too expensive or not able to satisfy the precision requirement, our laboratory is devoted to search for a special material with high machinability which can be machined to complex shapes with high precision under normal cutting conditions. In order to improve the research efficiency, a novel combinatorial method is been proposed.

Novel Thermographic Method for Characterizing Transformation Temperatures of Thin-Film Shape Memory Alloys Aimed at Combinatorial Approach

A novel characterization method for the two-way martensitic transformation temperatures of thin-film shape memory alloys (SMAs) is proposed. The method uses thermography to detect the transformation as a change in emissivity. The proposed method was demonstrated for a Ti–Pd–Ni thin-film SMA along with electrical resistivity monitoring. Definite emissivity changes were observed during both heating and cooling. Furthermore, the changes in emissivity corresponded to changes in the electrical resistivity. To confirm the validity of the proposed method, the results were compared with results obtained using conventional differential scanning calorimetry (DSC). The reverse-martensitic transformation temperature was found to agree with the results of the proposed method. However, the martensitic transformation temperature did not agree well. The reason for this disagreement is the differences in the definition of the transformation temperature and stress conditions used. We expect that the proposed method will enable high-throughput characterization of SMAs by a combinatorial approach in the future.

Novel Crystallization Temperature Measurement Method for Combinatorial Evaluation using Infrared Thermography

In combinatorial method, combinatorial evaluation of thin film library has not been established enough, so efficiency of searching by this method is limited. One of property which has not been available combinatorial evaluation is crystallization temperature (Tx). Conventionally, Tx is measured using differential scanning calorimeter (DSC), but it is impossible to apply to the thin film library. Because its one sample size is 1×1 mm, thickness is several micrometers, and 1,089 samples (33columns and 33 rows) are integrated on one library, so the samples are too small to measure using DSC. In this study, an alternative method using infrared thermography is presented for combinatorial evaluation of Tx. This device detects infrared energy radiated from an object and its temperature can be calculated using its own emissivity. In crystallization point, electrical resistivity change is lead with structure change, and this derives emissivity change. Low electrical resistivity means less free electron that is low reflectivity and high emissivity. In heating test, while emissivity keeps constant, T-Ta curve (T: true sample temperature, Ta: apparent temperature measured by thermography) gradient is constant, but the point of Tx, T-Ta curve gradient changes by change of emissivity. Therefore transformation point can be detected by T-Ta curve gradient change. This method can be applied to thin film library, because the method requires only observation of sample surface. PtSi and PdCuSi amorphous alloys were employed to confirm this method. First, homogeneous amorphous alloy thin films were deposited on alumina wafer (20×20mm). Each of these samples was then heated in vacuum chamber with monitoring infrared images and electrical resistivity, in-situ. Obvious emissivity change could be detected at the same temperature of electrical resistivity change. This temperature also agrees enough with DSC results. In case of Pt67Si33, emissivity change was detected at 511K, and DSC result shows Tx at 516K, there is only 5K error between these values. At this temperature, both electrical resistivity and emissivity decreased and it agrees with the theory. Sample crystallization was confirmed after heating test by X-ray diffraction. Measurement on the thin film library was then considered. A quarter thin film library was used, 256 samples (16×16) are integrated and each sample size is 1×1mm separated 0.2mm grid made by sputtering on alumina wafer. For first inspection, all samples were same composition PdCuSi amorphous alloy. Every 3×3 samples, center sample were blank, i.e. alumina surface, its emissivity is stable so the surface indicated reference temperature of around samples. Alumina emissivity was calibrated using a thermo couple on the sample wafer. 184 samples in the all samples were measured at one time, Tx can be detected in all 184 samples and these value errors ranged in 15K. Therefore, this method has a great of potential in combinatorial method.