Technique For In-line Monitoring Research Articles

Application of in-line Raman spectroscopy to monitor crystallization and melting processes in milk fat

Anhydrous milk fat (AMF) and its fractions are used as ingredients in a wide range of food applications. Obtaining the appropriate solid fat content (SFC) is essential to achieve the desired product texture. At present, in-line monitoring techniques to control milk fat crystallization and melting are largely unavailable. The thermal behaviour of milk fat (AMF and four of its fractions) was monitored in a temperature-controlled vessel using an in-line Raman analyser and compared with thermograms generated using differential scanning calorimetry (DSC). The major stages of milk fat crystallization and melting were identified using the in-line Raman analyser. Thermal data from DSC showed excellent linear correlations with Raman spectral data (R2 value of 0.97 for the onset of milk fat crystallisation). Partial least squares regression (PLSR) models were developed using Raman spectra to predict SFC with coefficient of determination (R2Cs) from 0.929 to 0.992 and root mean standard error of calibration (RMSECs) ranging from 3.20 to 10.36%. Results demonstrated Raman spectroscopy has significant potential as a way of monitoring milk fat crystallization and melting processes.

Implementation of Non Destructive Testing and in-line monitoring techniques on extra-large structures printed with WAAM technology

Grade2XL is a European project funded by the H2020 program that gathers 21 academic and industrial partners. Started in March 2020 for 4 years, the principal objective is to print extra-large structures using the WAAM (Wire Arc Additive Manufacturing) method with a complete control of the fabrication process. Since WAAM is a relatively new technology for printing large specimens, it is important to develop quality assurance methods that can be used during the fabrication and once the structure has been built, which is the focus of CEA List in the project. Regarding methods applied built structures, CEA List has investigated Resonant Ultrasound Spectroscopy (RUS) for the material characterization and more specifically the evaluation of the elastic constants or more conventional ones for the inspection with phased-array ultrasonic techniques (PAUT) or eddy current (EC) for the detection of indications are implemented and optimised them for the inspection of the final structures. Concerning the development of in-line monitoring methods, CEA List has been working on laser Doppler vibrometry (LDV) and X-ray fluorescence (XRF) spectrometry, in order to get structural information during the printing but also detect the appearance of abnormal events and correlate them to the appearance of defects generated during the WAAM process. This proceeding presents the advantages of those methods for the inspection of extra-large structures made by WAAM and discusses the first results obtained in the framework of the project. Keywords: Additive Manufacturing, NDT, Imaging techniques, Eddy current, In-line monitoring, laser vibrometry, X-ray fluorescence spectrometry, Resonant Ultrasound Spectroscopy.

Near Infrared Spectroscopy: A useful technique for inline monitoring of the enzyme catalyzed biosynthesis of third-generation biodiesel from waste cooking oil

Near Infrared (NIR) spectroscopy was used for inline monitoring the enzymatic production of third-generation biodiesel from waste cooking oil (WCO) —with fatty acid profile similar to olive oil— under the principles of Continued Process Verification (CPV) and Process Analytical Technology (PAT). For this purpose, covalently immobilized mature Rhizopus oryzae lipase (rROL) was used to transesterify WCO with methanol and ethanol, firstly in 10 mL vials under orbital stirring and then it was successfully scaled up to a mechanically stirred 50 mL laboratory reactor specially designed for use of a NIR probe. Biocatalyst half-life and productivity after ten reaction cycles with methanol and ethanol were assessed. Slightly higher operational stability with methanol (337.5 h, 54 batches) vs with ethanol (146.7 h, 44 batches) was observed, but decreased productivity as a result of the increased reaction times used with the former (219 vs 327 µmol min−1). The NIR spectroscopy results were highly correlated with those of gas chromatography (GC) used as reference. Thus, the root mean-square standard error of prediction (RMSEP) was 2.0% for methanol and 2.1% for ethanol. Therefore, NIR spectroscopy, which allows data acquisition in real time, is suitable for inline monitoring of enzymatic production of biodiesel.

In-Line Monitoring of Downstream Purification Processes for VSV Based SARS-CoV-2 Vaccine Using a Novel Technique.

The COVID-19 pandemic caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) increases the need for a rapid development of efficient vaccines. Among other vaccines in clinical trials, a recombinant VSV-∆G-spike vaccine was developed by the Israel Institute for Biological Research (IIBR) and is being evaluated. The development of an efficient downstream purification process (DSP) enables the vaccine to be advanced to clinical trials. The DSP must eliminate impurities, either process- or product-related, to yield a sufficient product with high purity, potency and quality. To acquire critical information on process restrictions and qualities, the application of in-line monitoring is vital and should significantly impact the process yield, product quality and economy of the entire process. Here, we describe an in-line monitoring technique that was applied in the DSP of the VSV-∆G-spike vaccine. The technique is based on determining the concentrations of metabolites, nutrients and a host cell protein using the automatic chemistry analyzer, Cobas Integra 400 Plus. The analysis revealed critical information on process parameters and significantly impacted purification processes. The technique is rapid, easy and efficient. Adopting this technique during the purification process improves the process yield and the product quality and enhances the economy of the entire downstream process for biotechnology and bio pharmaceutical products.

The potential of computer vision, optical backscattering parameters and artificial neural network modelling in monitoring the shrinkage of sweet potato (Ipomoea batatas L.) during drying.

Drying is a method used to preserve agricultural crops. During the drying of products with high moisture content, structural changes in shape, volume, area, density and porosity occur. These changes could affect the final quality of dried product and also the effective design of drying equipment. Therefore, this study investigated a novel approach in monitoring and predicting the shrinkage of sweet potato during drying. Drying experiments were conducted at temperatures of 50-70 °C and samples thicknesses of 2-6 mm. The volume and surface area obtained from camera vision, and the perimeter and illuminated area from backscattered optical images were analysed and used to evaluate the shrinkage of sweet potato during drying. The relationship between dimensionless moisture content and shrinkage of sweet potato in terms of volume, surface area, perimeter and illuminated area was found to be linearly correlated. The results also demonstrated that the shrinkage of sweet potato based on computer vision and backscattered optical parameters is affected by the product thickness, drying temperature and drying time. A multilayer perceptron (MLP) artificial neural network with input layer containing three cells, two hidden layers (18 neurons), and five cells for output layer, was used to develop a model that can monitor, control and predict the shrinkage parameters and moisture content of sweet potato slices under different drying conditions. The developed ANN model satisfactorily predicted the shrinkage and dimensionless moisture content of sweet potato with correlation coefficient greater than 0.95. Combined computer vision, laser light backscattering imaging and artificial neural network can be used as a non-destructive, rapid and easily adaptable technique for in-line monitoring, predicting and controlling the shrinkage and moisture changes of food and agricultural crops during drying. © 2017 Society of Chemical Industry.

Room Temperature Photoluminescence Characterization of Silicon Wafers for In-Line Monitoring Applications

Overall quality of the Si surface and dielectric/Si interface including cleanliness, passivation and surface recombination characteristics were characterized using room temperature photoluminescence (PL) spectroscopy. The spectral resolution and spatial resolution of PL spectroscopy are approximately 1 nm and tens of microns. To understand the depth distribution of electrically active defects/traps, at or near the Si surface and the dielectric/Si interface, different excitation wavelengths (with different probing depths) were used as the excitation light source. Significant variations in electrically active defects, traps, and contaminants, at or near the surface, and the dielectric/Si interface were found from Si with native oxide. Multiwavelength PL spectroscopy was also able to reveal electrically active defects and characteristics induced by the cleaning process and dielectric film deposition process steps. Multiwavelength PL spectroscopy is a promising and readily available technique for in-line monitoring of Si wafers at various stages of process.

In-line Monitoring of Grain Size Distribution of Channel Poly Si used in 3D NAND Flash Memory Devices using Multiwavelength Raman Spectroscopy

ABSTRACTFeasibility of multiwavelength Raman spectroscopy was studied as a potential in-line monitoring technique for grain size distribution in channel poly-Si used in three dimensional stacked NAND (3D NAND) Flash memory devices. Various channel poly-Si materials in 3D-NAND Flash memory devices, converted from chemical vapor deposition (CVD) grown a-Si, were characterized using non-contact, multiwavelength Raman spectroscopy and high resolution cross-sectional transmission electron microscopy (HRXTEM). The Raman characterization results were compared with HRXTEM images. The correlation between the grain size distribution characterized by multiwavelength Raman spectroscopy and “on current” (ION) of 3D NAND Flash memory devices was investigated. Good correlation between these techniques was seen. Multiwavelength Raman spectroscopy is very promising as a non-destructive in-line monitoring technique for grain size distribution in channel poly-Si used in 3D NAND Flash memory devices.

Room Temperature Photoluminescence Characterization of Interface Quality of SiN/SiO2/Si Prepared under Various Deposition Techniques and Conditions

Room temperature photoluminescence (RTPL) spectroscopy was examined as an in-line monitoring technique for characterizing the interface of ultra-thin (~7.2 nm) stacked dielectric films (SiN/SiO2) on 300 mm Si wafers. To investigate the effect of the stacked dielectric films on electronic properties at the interface, RTPL signals were measured under various excitation wavelengths with different probing depths. Changes of interface quality of the stacked dielectric films and the Si wafer were investigated using various specimens prepared by different deposition techniques and conditions. The overall interface quality of the SiN/SiO2/Si specimens was found to be very dependent on the SiN deposition technique and process conditions. N-rich SiN films resulted in very intense RTPL signals. As the stoichiometry of SiN films change from N-rich to Si-rich conditions, the RTPL signal becomes weaker, indicating the change of electronic properties at the SiN/SiO2/Si interface. Within-wafer and wafer-to-wafer variations of the SiN/SiO2/Si interface quality were successfully characterized by RTPL spectroscopy under various excitation wavelengths.

Room Temperature Photoluminescence and Raman Characterization of Interface Characteristics of SiN/SiO2/Si Prepared under Various Deposition Techniques and Conditions

Room temperature photoluminescence (RTPL) spectroscopy and Raman spectroscopy were examined as in-line monitoring techniques for characterizing the interface characteristics of ultra-thin (∼7.2 nm) stacked dielectric films (SiN/SiO2) on 300 mm Si wafers. To investigate the effect of the stacked dielectric films on electronic properties and lattice stress of Si beneath the films, RTPL and Raman signals were measured under various excitation wavelengths with different probing depths. Changes of interface characteristics (mainly, electronic properties and lattice stress of Si beneath the films) of the stacked dielectric films and the Si wafer were investigated using various specimens prepared by different deposition techniques and conditions. The overall interface characteristics of the SiN/SiO2/Si specimens was found to be very dependent on the SiN deposition technique and process conditions. As the stoichiometry of SiN films change from N-rich to Si-rich conditions, the RTPL signal becomes weaker, indicating the change of electronic properties at the SiN/SiO2/Si interface. Within-wafer and wafer-to-wafer variations of the SiN/SiO2/Si interface characteristics were successfully characterized by RTPL and Raman spectroscopy under various excitation wavelengths. Other characterization results such as film thickness from ellipsometry, film stress from wafer curvature and film composition from Auger electron spectroscopy (AES) were also discussed.

Dielectric/Si Interface Quality Characterization Using Room Temperature Photoluminescence

Room temperature photoluminescence (RTPL) spectroscopy was proposed as an in-line monitoring technique for characterizing the dielectric/Si interface. Specifically, Si lattice stress beneath dielectric films and overall quality of the dielectric/Si interface (including passivation characteristics) are investigated. As an application example, ~7.0 nm thick ultra-thin SiO2 films on 300 mm Si wafers, prepared by various oxidation techniques and conditions, were characterized using multiwavelength RTPL spectroscopy. The overall SiO2/Si interface quality was seen to be very dependent on oxidation technique and process condition. Within wafer and wafer-to-wafer variations of SiO2/Si interface quality were successfully characterized by RTPL spectrum measurement and intensity wafer mapping under different excitation wavelengths.

Ultra-Thin SiO2/Si Interface Quality In-Line Monitoring Using Multiwavelength Room Temperature Photoluminescence and Raman Spectroscopy

Multiwavelength room temperature photoluminescence (RTPL) and Raman spectroscopy were proposed as in-line monitoring techniques for characterizing the dielectric/Si interface. As an application example, ∼7.0 nm thick ultra-thin SiO2 films on 300 mm Si wafers, prepared by various oxidation techniques and conditions, were characterized using multiwavelength RTPL and Raman spectroscopy. Specifically, overall quality of the ultra-thin SiO2/Si interface (including passivation characteristics) and Si lattice stress beneath SiO2 films are investigated. The overall SiO2/Si interface quality was seen to be very dependent on oxidation technique and process conditions. Within wafer and wafer-to-wafer variations of SiO2/Si interface quality were successfully characterized by RTPL and Raman spectra measurements. For electrical analysis of SiO2/Si-based structures, non-contact corona charge-based, in-line (capacitance-voltage (C-V) and stress induced leakage current (SILC)) measurements were performed and compared with RTPL and Raman characterization results. Surprisingly, significant variations in RTPL intensity at and near the corona charge-based measurement sites, indicated that the corona-based electrical measurement technique, though non-contact, was indeed invasive. The effect of corona-charge based electrical measurements on SiO2/Si interface was permanent and even clearly visible from the back side of the wafer. RTPL intensity variations at and near the measurement sites remained, even after a forming gas anneal.

Formation and Characterization of Nickel Germanosilicide on Si1-xGex/Si/SiO2/Si

TiN capped Ni/Si1-xGex/Si/SiO2/Si wafers are prepared to investigate the formation of nickel germanosilicides in the temperature range of 235oC ~ 400oC in 1 atm N2. The annealing was done in a stacked hotplate system for 10 min (wafer residence time in the heater chamber). The Ge content of 80 nm-thick Si1-xGex layers was varied between 15 and 30 at%. Sheet resistance of thin film stacks were measured using a four point probe as a function of annealing temperature and Ge content. Multiwavelength micro-Raman measurements and X-ray diffraction measurements were performed to investigate crystallographic phases and reaction mechanisms of resulting nickel germanosilicides. Excitation wavelength dependence of Raman measurements was found and optimum excitation wavelength was experimentally determined. Clear correlation among sheet resistance, X-ray diffraction and Raman spectra was found as a function of annealing temperature and Ge content. A combination of X-ray diffraction and multiwavelingth micro-Raman spectroscopy was found to be very promising as in-line monitoring techniques.

Ultrasonic in-line monitoring of styrene miniemulsion polymerization

Ultrasonic transmission is a simple, non-destructive method to characterize turbid systems like e.g. emulsions or polymer dispersion. Here we use this technique for in-line monitoring of the miniemulsion polymerization of styrene. Either the ultrasound attenuation or the velocity signal provides a fingerprint characterizing the reaction process. During the reaction process the sound velocity increases by about 150m/s and the attenuation coefficient α changes by more than 75%. In the early stage of polymerization the thermoelastic effect dominates α and accordingly α decreases when more and more polymer chains are generated. In this regime the fractional conversion of monomer to polymer X is obtained from a calibration of the α values using gravimetrically determined X data. In the later stage of the process polymer relaxation dominates and α goes through a sharp maximum when the reaction temperature matches the dynamic glass transition temperature Tg,dyn of the polymer/monomer mixture within the droplets. Then X can be directly calculated from Tg,dyn without calibration only using physical material parameters for the given monomer/polymer system, and the corresponding data are in excellent agreement with gravimetrically determined values.This method may be applied to the emulsion polymerization of other monomers, but also for monitoring solution polymerization processes as long as the reaction temperature TR is below Tg,dyn. In case of emulsion polymerization the initial decay of α may also be used for process control for systems, which exhibit a change in thermoelastic contrast during polymerization, even if TR>Tg,dyn, but needs additional calibration.

Multiwavelength Micro-Raman Characterization of Epitaxial Si1−x Ge x Layers on Si(100) and In-Line Process Monitoring Applications

Undoped and B-doped epitaxial Si1−x Ge x layers on Si(100) were characterized using a long-focal-length, polychromator-based, multiwavelength micro- Raman spectroscopy system. The peak position and full-width at half-maximum of the Si–Si signal from Si1−x Ge x correlates very strongly with Ge content and B concentration. The intensity ratio of the Si–Si peak from the epitaxial layer to the Si peak from the substrate indicates the thickness of the epitaxial Si1−x Ge x layer. Raman characterization results were confirmed by both high-resolution x-ray diffraction and secondary-ion mass spectroscopy. Multiwavelength Raman spectroscopy was used as a practical, noncontact, in-line monitoring technique for Si1−x Ge x epitaxial processes during device manufacture.

Inline monitoring the effect of chemical inhibitor on the calcium carbonate precipitation and agglomeration

The formation of mineral scale particularly calcium carbonate is a problem for industries ranging from oil and gas to desalination plants. Various techniques have been studied to prevent the formation of scale. The use of chemical inhibitors to prevent calcium carbonate agglomeration is widely studied. The present study attempts to show that the inline monitoring technique is a useful tool for laboratory experimental investigation of agglomeration phenomenon. This method is successful in providing the induction time of starting agglomeration. It was shown that the presence of inhibitor delays the agglomeration and affects the deposition of calcium carbonate. In addition the method is found useful in determining the minimum inhibitor concentration and also to screen various types of inhibitors for the selection. The influence of an inhibitor is studied on scaling solution of various calcium ion concentrations. Finally, the result of inline technique was validated by comparing with the conventional one called offline technique. The SEM images reveal that the mechanism of inhibition might be the surface adsorption or distortion of inhibitor molecules on the growing calcium carbonate crystals.

In-line monitoring technique with visible light from 13 μm-band SHG module for optical access systems

We propose an in-line monitoring technique that uses 650 nm visible light for performing maintenance work on Fiber-to-the-home (FTTH) network quickly without the need for measuring skills or external devices. This technique is characterized by visible light (650 nm) generated by an SHG module from the 1.3 microm-band line signal. We fabricate a 1.3 microm-band quasi phase matched LiNbO(3) (QPM-LN) module, and the measure the 650 nm second harmonic (SH) power to test the proposed short-pulse modulation method. The results confirm the feasibility of the short-pulse modulation method with different peak factors (PFs) (1.0-7.3). We also examine the effect of short-pulse modulation on system performance at the optical receiver by measuring the bit error rate (BER) of received data (1.25 Gb/s). The BER is basically unaffected by the PF (1.0-5.5). This means that the proposed technique has little influence on data reception as regards PF (1.0-5.5).

Dynamic Parameters Estimation Method: Advanced Manometric Temperature Measurement Approach for Freeze-Drying Monitoring of Pharmaceutical Solutions

The aim of this paper is to describe and validate the dynamic parameters estimation (DPE) method, a noninvasive in-line monitoring technique for the freeze-drying process of pharmaceuticals that on...

Process monitoring of polymer melts using in-line spectroscopy

Over the last decade, there has been an increased drive in the polymer industry toward the development of in-line monitoring techniques for analysis of melt processing. Manufacture of high material volumes combined with stringent quality-control restrictions and the requirement for tailored end-user products, have made the implementation of analytical methods essential for measurement of material characteristics. This paper presents the application of a range of spectroscopic techniques for in-line analysis of polymer extrusion processes. Fourier transform near-infrared (FT-NIR), Raman and fluorescence spectroscopy have been successfully implemented as tools to monitor a range of processing characteristics including copolymer melt and additive composition, material residence time distribution and degree of polymerization. In combination with partial least squares (PLS) chemometric analysis, these spectroscopic techniques are demonstrated to be sensitive and robust tools for monitoring a wide range of chemical and physical parameters at high-temperature and pressure in a polymer-processing environment.

IN-PROCESS MONITORING OF FEMTOSECOND LASER MATERIAL PROCESSING

Recent research and development on the femtosecond laser has shown that it is a powerful tool for high precision micromachining. However, the femtosecond laser-material interaction is fast and complex due to its ultrashort pulse duration. Consequently, it is not an easy task to optimize process parameters and to ensure high-quality fabrication. In this context, we propose an in-line monitoring technique based on plasma plume diagnostics. By analyzing the spectra of the femtosecond laser-induced plasma, which was detected and analyzed using a spectrometer, the plasma temperature of the copper sample was estimated. As drilling holes and cutting lines are two common applications in industry, the relationship between the emission light and the geometry of the fabricated structure was investigated based on the time-varying signals from the photodetector. These results will help us to understand the mechanism of femtosecond laser ablation so as to achieve high quality micromachining.

Ultrasonic sensor and technique for in-line monitoring of die castingprocess

An ultrasonic clad steel buffer rod sensor embedded in the die hasbeen used to in-line monitor the die casting process using aluminium alloybillets with semi-solid (thixotropic) and dendritic microstructures asfeedstocks. This clad steel buffer rod provided better performance than thepreviously reported clad zirconium buffer rod. A multiple recording techniquewas used for the fast data acquisition with a rate up to 0.003 s peracquisition. This single ultrasonic probe monitored the completion of the diefilling, the release of the pressure, the opening of the die, part detachmentand solidification of the part. The change of the ultrasonic travel time inthe clad buffer rod and cast part relates to the variation of the averagetemperature in the die and part, respectively. The measured amplitude profileof the reflected echo at the probe end/cast part interface can be used tomonitor the cold shot and complete filling. The variation of the ultrasonicattenuation coefficient in the cast part may also relate to the change of thecomposition, microstructure and porosity.