Non-contact temperature measurement of silicon wafers based on the combined use of transmittance and radiance

We propose a non-contact temperature measurement method that combines the temperature dependence of transmittance below 600 °C and radiation thermometry above 600 °C. The combined method uses a polarization technique and the Brewster angle between air and a dielectric film such as SiO₂ or Si₃N₄ grown on silicon wafers. A prominent feature of this method is that both measurements of transmittance and radiance are performed with the same geometrical arrangement.For a semitransparent wafer, the measurement of p-polarized transmittance at the wavelengths of 1.1, 1.2 and 1.3 μm enables temperature measurement in the range from room temperature to 600 °C. For an opaque wafer above 600 °C, the p-polarized radiation thermometry at the wavelength of 4.5 μm allows the temperature measurement without the emissivity problem. The combined method with the use of transmittance and radiance is valid in the entire temperature range irrespective of variations of film thickness and resistivity.     

Tribological behavior and wear mechanisms of MoSi2-base composites sliding against AA6063 alloy at elevated temperature

Intermetallic Mo(Si,Al)₂, Mo(Si,Al)₂/Al₂O₃, Mo(Si,Al)₂/SiC and Mo(Si,Al)₂/ZrO₂ composites produced by spark plasma sintering of mechanically alloyed powders were tested on a block-on-cylinder apparatus, sliding against an AA6063 alloy cylinder at elevated temperature. Abrasion, micro-fracture and surface tribochemical reactions were found to be the operative wear mechanisms, producing severe wear in the investigated alloys. Abrasive wear by pull-out of Al₂O₃ and micro-fracture of Mo(Si,Al)₂ particles promotes severe wear in the Mo(Si,Al)₂/Al₂O₃ composite. In the Mo(Si,Al)₂/SiC composites, hard SiC inclusions suppressed the abrasive wear, but a tribochemical reaction was found to be the dominant wear mechanism. A combination of abrasion by pull-out of Al₂O₃ particles and a tribochemical reaction was revealed to be the main wear mechanism in the Mo(Si,Al)₂/ZrO₂ materials. The brittleness index B = H/K_1C was applicable for prediction of the relative wear resistance. In agreement with the suggested model, the lowest wear rate, corresponding to B = 5.5–6.5 μm^−1/2, was found in the Mo(Si,Al)₂/30 vol.% SiC and Mo(Si,Al)₂/30 vol.% ZrO₂ composites.     

Tribological behavior of NiAl matrix composites with addition of oxides at high temperatures

NiAl, NiAl–Cr–Mo alloy and NiAl matrix composites with addition of oxides (ZnO/CuO) were fabricated by powder metallurgy route. It was found that some new phases (such as NiZn₃, Cu_0.81Ni_0.19 and Al₂O₃) are formed during the fabrication process due to a high-temperature solid state reaction. Tribological behavior was studied from room temperature to 1000 °C on an HT-1000 ball-on-disk high temperature tribometer. The results indicated that NiAl had high friction coefficient and wear rate at elevated temperatures, while incorporation of Cr(Mo) not only enhanced mechanical properties evidently but also improved high temperature tribological properties. Among the sintered materials, NiAl matrix composite with addition of ZnO showed the lowest wear rate at 1000 °C, while CuO addition into NiAl matrix composite exhibited the self-lubricating performance and the best tribological properties at 800 °C.     

Mechanical and tribological properties of NiCr–Al2O3 composites at elevated temperatures

The effect of Al₂O₃ content on the mechanical and tribological properties of Ni–Cr alloy was investigated from room temperature to 1000 °C. The results indicated that NiCr–40 wt% Al₂O₃ composite exhibited good wear resistance and its compressive strength remained 540 MPa even at 1000 °C. The values obtained for flexural strength and fracture toughness at room temperature were 771 MPa, 15.2 MPa m^1/2, respectively. Between 800 °C and 1000 °C, the adhesive and plastic oxide layer on the worn surface of the composite was claimed to be responsible for low friction coefficient and wear rate.     

Tribological characterisation of siliconcarbonitride ceramics derived from preceramic polymers

Amorphous SiCN ceramics were prepared in a laboratory scale as disk shaped specimens with 10 mm diameter and 0.3 mm thickness. The friction and wear behaviour was characterised in gross slip fretting tests under unlubricated conditions at room temperature against steel (100Cr6) and ceramic (Al₂O₃). Tests with a ball-on-disk contact were performed in laboratory air with different content of water vapour. The results show clearly that the relative humidity has a significant effect on friction and wear behaviour. All tests in dry air lead to higher friction and higher wear rate than in normal air. Improved friction and wear behaviour was observed with increasing pyrolysis temperature up to 1100 °C of the SiCN specimens. This is attributed to increasingly better mechanical properties and higher stiffness of the amorphous network due to the evaporation of gaseous organic species and the formation of free graphite like carbon.     

Plastic deformation of 25CrMo4 steel during wear: Effect of the temperature,the normal force,the sliding velocity and the structural state

This article follows a previous study on friction and wear of 25CrMo4 steel [N. Khanafi-Benghalem, K. Loucif, E. Felder, F. Delamare, Influence de la température sur les mécanismes de frottement et d’usure des aciers X12NiCrMoSi25-20 et 25CrMo4 glissant sur du carbure de tungstène, Matériaux et techniques 93 (2005) 347–362]. The aim of our work is to study in more details the process of plastic deformation and the wear rate of this steel in lubricated sliding against cemented tungsten carbide, process observed in the previous work. The considered parameters are the temperature T (from 20 to 200 °C), the normal force P (from 500 to 1500 N), the steel structure (normalised HV 220 and quenched/tempered HV 480 states) and the sliding velocity v (from 0.05 to 0.3 m/s). We measured the friction coefficient and the sample total volume loss. A displacement sensor follows the volume loss evolution during the test; this follow-up is approximate because of the sample plastic flow which leads to the formation of peripheral burrs. All the tests conditions generate a significant plastic deformation of the sample steel, even in the quenched/tempered state: it produces a marked increase of the surface hardness, the work hardened layer being much finer for the quenched/tempered state (15 μm) than for the normalised state (40 μm at 20 °C). For temperatures T ≤ 100 °C in normalised state, the wear follows the Archard's law with an increasing rate with temperature. For T ≥ 120 °C, the wear rate decreases during the test, the global volume of wear being a decreasing function of T. For the quenched/tempered state, the wear rate decreases with the increase of the normal force, this decrease is less than 30% of the normalised state value. The material heating during the wear tests is well correlated with the friction dissipated power, but remains small, except in extreme cases (v maximum, great friction at high temperatures). These results suggest the existence of two wear mechanisms: abrasion by sample debris and burrs emission by plastic flow. The abrasion is probably the dominating mechanism for the tests carried out at the lowest temperatures. The plastic flow becomes a significant component at the highest temperatures. Using a contact model, we discuss to what extent the influence of the temperature and the strain rate on the steel hardness and ductility could explain the temperature and the sliding velocity effect on wear. Other phenomena are probably present: the influence of the steel microstructure and the lubricant on the size and/or the number of particles responsible for abrasion.     

Effect of CuO as a dopant in TiO2 on ammonia and hydrogen sulphide sensing at room temperature

The heterogeneous nanocomposites of CuO doped TiO₂ nanoparticles were synthesized using sol gel method by varying the concentration of CuO as 0.1, 0.5 and 1 mol% for the sensing of ammonia and hydrogen sulphide. The substitutional doping of CuO in TiO₂ matrix was confirmed by the X-ray diffraction. Average crystallite size of the doped nanocomposites was found to reduce with increase in concentration of CuO. The 0.1 mol% CuO doped TiO₂ nanocomposites showed highest sensitivity to ammonia (97%) with response time of 2 s, while 1 mol% was selective to H₂S gas (77%) with response time of 45 s for 50 ppm of each gas at room temperature.     

Tribological properties of NiCr–Al2O3 cermet-based composites with addition of multiple-lubricants at elevated temperatures

The tribological properties of NiCr-40 wt% Al₂O₃ (NC40A) cermet-based composites containing SrSO₄ and other lubricant (graphite, MoS₂ and Ag) against alumina ball were evaluated to identify their self-lubrication mechanisms from room temperature to 800 °C. The composites demonstrated distinct improvements in effectively reducing friction and wear, as compared to NC40A cermet. The best results were observed for NC40A–10SrSO₄–10Ag composite, which exhibited satisfactory reproducibility of friction coefficient over a wide temperature range (200–800 °C) through high temperature cyclic friction tests due to the formation of synergistic lubricating films SrAl₄O₇, NiCr₂O₄ and Ag on the contact surface.     

Wear characteristics of Cr3C2–NiCr and WC–Co coatings deposited by LPG fueled HVOF

Wear behavior of the HVOF deposited Cr₃C₂–NiCr and WC–Co coatings on Fe-base steels were evaluated by the pin-on-disc mechanism. The constant normal load applied to the pin was 49 N and sliding distance was 4500 m with velocity of 1 m/s, at ambient temperature and humidity. The specific wear rate of WC–Co coating was 3 mm³/N m and Cr₃C₂–NiCr coating was 5.3 mm³/N m. SEM/EDAX and XRD techniques were used to analyze the worn out surface and wear debris. The Fe₂O₃ was identified as the major phase in the wear debris. The wear mechanism is mild adhesive wear in nature.     

A comparative study on the wear properties of coarse-grained Al6061 alloy and nanostructured Al6061–Al2O3 composites

Wear behavior of nanostructured Al6061 alloy and Al6061–Al₂O₃ nanocomposites produced by milling and hot consolidation were investigated. The samples were characterized by hardness test, pin-on-disk wear test, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Nanocomposites containing 3 vol% Al₂O₃ showed a maximum hardness of 235 HV and optimum wear rate of 4×10⁻³ mg/m. Increasing the amount of Al₂O₃ up to 5 vol% resulted in decrease in hardness values (∼112 HV) and a sharp rise in wear rate (∼18×10⁻³ mg/m).     

Spray pyrolysed Mn:Co3O4 thin film electrodes via non-aqueous route and their electrochemical parameter measurements

Present work explains the preparation of manganese incorporated cobalt oxide thin film electrodes on stainless steel by spray pyrolysis technique, via non-aqueous (methanolic) media. Structural, morphological and electrochemical characterizations of the prepared samples were made by means of XRD, SEM and electrochemical measurements. Structural elucidation confirms Co₃O₄ has face centred cubic and Mn₃O₄ has tetragonal body centred cubic structure with polycrystalline nature. Surface morphological observation shows the continuous semi porous film growth with spherical grains. Cyclic voltammetry reveals the mixed capacitive behaviour with maximum specific capacitance 605.35 F/g at the scan rate 1 mV/s in 1 M KOH electrolyte. Chronopotentiometric measurement gives energy density 33.5 Wh/kg, power density 2 kW/kg and Columbic efficiency 99.23%. Electrochemical impedance study was carried out in the frequency range 1 mHz to 1 MHz to see the internal resistance. Randles equivalent circuit was developed by using ZsimpWin software to search the circuitry parameters associated with the cell.     

Sliding wear of silicon carbide modified by etching with chlorine at various temperatures

The effect of reaction temperature on the formation of a carbon layer on the surface of SiC has been investigated. Subsequently, the tribological properties of the formed carbon layers were studied. The experimental procedure involved exposing reaction-bonded SiC balls to a flowing gas mixture of 5% Cl₂, 2.5% H₂, and Ar at a high temperature of 800, 1000, or 1200 °C. A ball-on disk tribometer was used to investigate the friction and wear behavior of the treated specimens. While partially unreacted SiC phases were observed in the layer modified at 800 °C, rhombohedral graphite crystals were formed in the layer modified at 1200 °C. Compared to untreated SiC, the treated SiC materials were found to have relatively low friction coefficients and better wear resistance. Increasing the treatment temperature was found to improve the tribological performance of the resulting surface-modified SiC balls. A possible reason for this tribological improvement has been discussed based on the observed carbon phases.     

Microstructure and wear resistance of low temperature hot pressed TiB2

Fine-grained TiB₂ compacts have been hot pressed to 98–99% theoretical density at 1400 °C. The compacts were consolidated from sub-micron powders prepared by a high-energy ball milling technique. Titanium diboride (TiB₂) powders were obtained from the milling of commercially synthesized TiB₂ and also from the mechanical alloying (MA) of Ti and B precursors. The formation of TiB₂ from Ti and B powders by mechanical alloying was found to reach completion after 3 h, and wear debris from steel mill vials and media introduced 0.8 to 1.5 wt% Fe in the sintered compacts. The dry erosion resistance of the highest density compacts was examined using an ASTM standard test with an abrasive jet of Al₂O₃ impinging at a normal angle of incidence. Steady-state erosion rates of 0.5 mm³/kg of erodent compare favorably with the measured value of 9 mm³/kg for commercial, fine-grained WC–Co cermets under identical conditions. Microstructures, fracture surfaces, and erosion craters were also examined by electron microscopy.     

Studies on wear behavior of nano-intermetallic reinforced Al-base amorphous/nanocrystalline matrix in situ composite

Resistance to wear is an important factor in design and selection of structural components in relative motion against a mating surface. The present work deals with studies on fretting wear behavior of in situ nano-Al₃Ti reinforced Al–Ti–Si amorphous/nanocrystalline matrix composite, processed by high pressure (8 GPa) sintering at room temperature, 350, 400 or 450 °C. The wear experiments were carried out in gross slip fretting regime to investigate the performance of this composite against Al₂O₃ at ambient temperature (22–25 °C) and humidity (50–55%). The highest resistance to fretting wear has been observed in the composites sintered at 400 °C. The fretting wear involves oxidation of Al₃Ti particles in the composite. A continuous, smooth and protective tribolayer is formed on the worn surface of the composite sintered at 400 °C, while fragmentation and spallation leads to a rougher surface and greater wear in the composite sintered at 450 °C.     

Effect of SiC particles on the friction and wear behavior of Ti3Si(Al)C2-based composites

The non-lubricated, sliding friction and wear behavior of Ti₃Si(Al)C₂ and SiC-reinforced Ti₃Si(Al)C₂ composites against AISI 52100 bearing steel ball were investigated using a ball-on-flat, reciprocating tribometer at room temperature. The contact load was varied from 5 to 20 N. For monolithic Ti₃Si(Al)C₂, high friction coefficients between 0.61 and 0.90 and wear rates between 1.79 × 10⁻³ and 2.68 × 10⁻³ mm³ (N m)⁻¹ were measured. With increasing SiC content in the composites, both the friction coefficients and the wear rates were significantly decreased. The friction coefficients reduced to a value between 0.38 and 0.50, and the wear rates to between 2.64 × 10⁻⁴ and 1.93 × 10⁻⁵ mm³ (N m)⁻¹ when the SiC content ranged from 10 to 30 vol.%. The enhanced wear resistance of Ti₃Si(Al)C₂ is mainly attributed to the facts that the hard SiC particles inhibit the plastic deformation and fracture of the soft matrix, the oxide debris lubricate the counterpair, and the wear mode converts from adhesive wear to abrasive wear during dry sliding.     

Improved wear resistance in alumina-PTFE nanocomposites with irregular shaped nanoparticles

Past studies with PTFE nanocomposites showed up to 600× improvements in wear resistance over unfilled PTFE with the addition of Al₂O₃ nanoparticles. Irregular shaped nanoparticles are used in this study to increase the mechanical entanglement of PTFE fibrils with the filler. The tribological properties of 1, 2, 5 and 10 wt.% filled samples are evaluated under a normal pressure and sliding speed of 6.3 MPa and 50.8 mm/s, respectively. The wear resistance was found to improve 3000× over unfilled PTFE with the addition of 1 wt.% nanoparticles. The 5 wt.% sample had the lowest steady state wear rate of K = 1.3 × 10⁻⁷ mm³/N m and the lowest steady friction coefficient with μ = 0.21.     

Characteristics of MSM photodetector fabricated on porous In0.08Ga0.92N

In this study, nanoporous structures of In_0.08Ga_0.92N thin films were synthesized using anodic etching at various etching durations. The metal–semiconductor–metal photodetectors subsequentaly have been fabricated by depositing a high work function metal (Pt) on the thin films. Results show that the responsivity of the detector increased with increasing the etching duration to reach to the maximum value at 15 min. Moreover, the rise and recovery times of the device were investigated at 390 nm chopped light.     

Lubricating property of MQL grinding of Al2O3/SiC mixed nanofluid with different particle sizes and microtopography analysis by cross-correlation

With the increased requirements for environmental protection, energy conservation, and low consumption, nanofluid minimal quantity lubrication (MQL) grinding, which is an environment-friendly machining method, has been paid increasing attention. Improving the lubricating property of nanofluids effectively is currently a main research trend. Meanwhile, optimizing mixed nanoparticle (NP) size ratio is an effective way for enhancing the lubricating property of MQL grinding. In the experiment, different sizes (30, 50, and 70 nm) of Al₂O₃ and SiC NPs were mixed, and nanofluids were prepared at 2% (volume fraction) mixed NPs and base oil. The prepared nanofluids were then used in MQL grinding on a hard Ni-based alloy (inconel 718). The experiment was then evaluated by specific grinding force, removal rate of workpiece, surface roughness, morphology of grinding debris, and contact angle. The effect of the sizes of the Al₂O₃/SiC mixed NPs on MQL grinding performance was discussed in accordance with the period and amplitude, as well as cross-correlation coefficient, of the workpiece surface cross-correlation function curve profile. Experimental results suggest that different Al₂O₃/SiC mixed NP sizes affect the nanofluid MQL grinding performance variably. The highest removal rate of the workpiece [189.05 mm³/(s N)] and the lowest RSm (0.0381 mm) were achieved when the Al₂O₃/SiC mixed NP size ratio was 70:30. The lowest Ra (0.298 μm) was obtained at 50:30. Meanwhile, the highest length ratio of the profile support (90%), the best morphology of abrasive dusts, and the largest wetting area of liquid drops were acquired at 30:70. Furthermore, a cross-correlation analysis of the workpiece surface profile curve under three size ratios (30:70, 50:30, and 70:30) was carried out. The cross-correlation function curve of the workpiece surface profile under 30:70 attained the shortest period, the largest amplitude, and the largest cross-correlation coefficient (0.67), thereby indicating good workpiece surface quality. Therefore, 30:70 was the best size ratio of the Al₂O₃/SiC mixed nanofluid.     

Temperature control system for laser heating: Application for minute asteroidal materials

A temperature control system for a laser heating has been developed to extract noble gases from minute material samples recovered from the asteroid Itokawa by the Hayabusa spacecraft. An ultra-fine thermocouple was produced from 3% Re–W and 26% Re–W wires 25 μm in diameter, and its electromotive force was calibrated. A temperature control program was originally produced using LabVIEW 2011 in which proportional-integral-derivative (PID) control was not adopted as an algorithm of the program. Particle samples smaller than 60 μm in diameter were set in conical depressions in a sample holder made of fused silica and irradiated by a slightly defocused Nd-YAG laser. The temperature of the samples was recorded by the thermocouple that passed through a small hole 50 μm in diameter because the sample and the thermocouple always came into contact during laser heating. The program controlled the temperature of the tiny samples appropriately. The average temperature during heating was slightly lower than the setting temperature and the standard deviation and the maximum overshoot were lower than 2.5% and 6.0% of the setting temperature, respectively. The performance of the temperature control system is high enough to conduct the stepwise heating experiment for minute extraterrestrial material samples.     

A study on erosion of upper bainitic ADI and PDI

Ductile iron containing ∼3.5 wt.% C and 2.1–4.2 wt.% Si (2.1, 2.8 and 4.2 wt.%) was studied. Three sets of specimens with differing Si contents were made into austempered ductile iron (ADI) and pearlite ductile iron (PDI) through heat treatment. These specimens were then eroded with Al₂O₃ particles and SiO₂ particles of 275–295 μm grit size to understand the relationship between erosion rate and microstructure. The ADI specimens were upper bainitic matrices that were austempered for different periods of time at 420 °C. The heat treatment of PDI was conducted at 870 or 930 °C for 1 h then forced air cooled or oil quenched to room temperature.Two types of wear curves, single peak curves and double peak curves, were found when plotting the erosion rate figures derived from the experimental results. 2.1 wt.% Si and 2.8 wt.% Si ADI tempered for a long period of time, due to their decreased retained austenite content and increased carbide content, had a single peak erosion rate curve. This embrittlement effect caused the impact angle of maximum erosion rate to increase from ∼30 to ∼45°. Decreasing the interspacing of the lamellae cementite promoted the hardness and improved the low-angle erosion wear resistance of PDI. The high hardness and brittleness of the matrix reduces the high-angle erosion resistance and the peak erosion rate occurs at a higher angle.For 2.1Si-ADI and 2.8Si-ADI tempered for a short duration, increasing the volume fraction of martensite in the matrix increases the erosion rate at an impact angle of 30°, but the maximum erosion rate is found at 75°. This results in a curve with a double peak. The double peak curve was also observed for high silicon ADI tempered for a long duration. The high solid solution hardness of 4.2Si-ADI, due to low retained austenite content and the presence of carbide in the matrix, results in poor erosion resistance. When this material is austempered for a long period, the erosion rate curve shifts from a single peak curve (30°) to a double peak curve (30°; 60°).