Industries

Aerospace & Defense

EAG is your R&D partner, working with aerospace and defense manufacturers and suppliers to create faster, safer and more reliable aircraft and components. We use the most advanced…

EAG is your R&D partner, working with aerospace and defense manufacturers and suppliers to create faster, safer and more reliable aircraft and components. We use the most advanced analytical methodologies to answer complex engineering, materials and manufacturing problems, from evaluating the purity of new materials to confirming the characteristics of ceramic matrix composites. For research, development and production, we work alongside your technical staff to formulate and troubleshoot the next generation of aerospace and defense materials.

Chemicals & Basic Materials

For over 50 years, EAG’s scientists have applied advanced analytical techniques to solve tough problems and support R&D activities for manufacturers and users of a wide variety…

For over 50 years, EAG’s scientists have applied advanced analytical techniques to solve tough problems and support R&D activities for manufacturers and users of a wide variety of chemicals and materials. EAG offers reliable analytical results, development support for novel products, and answers to complex problems for manufacturers of chemicals used in metals, fibers, plastics, coatings, adhesives, construction materials, textiles, lubricants and more.

Consumer Products

Consumer products manufacturers and partners turn to EAG to answer R&D questions, ensure supply chain quality, respond to regulatory requirements and ensure well-supported legal…

Consumer products manufacturers and partners turn to EAG to answer R&D questions, ensure supply chain quality, respond to regulatory requirements and ensure well-supported legal arguments. EAG scientists have helped all types of consumer products companies accelerate innovation, resolve manufacturing concerns and comply with evolving regulations.

Food & Agriculture

Drive R&D productivity and keep pace with evolving environmental regulations. From agrochemical development to evaluating innovative packaging solutions, EAG scientists support…

Drive R&D productivity and keep pace with evolving environmental regulations.

From agrochemical development to evaluating innovative packaging solutions, EAG scientists support the agriculture/food s industry with scientific expertise required to enhance shelf life, ensure product safety and understand environmental impact. Whether in need of food quality investigations or help supporting regulatory filing of new chemicals, ask EAG. WE KNOW HOW.

Law

When a business’s brand and reputation is at stake, clients turn to EAG’s litigation support services for dependable scientific answers. Since 1959, our scientific expertise,…

When a business’s brand and reputation is at stake, clients turn to EAG’s litigation support services for dependable scientific answers. Since 1959, our scientific expertise, testing and testimony have supported legal strategies for intellectual property, product liability and insurance cases. Our scientists offer expertise in technology, life sciences, electronics, industrial and consumer products, having tested a broad array of materials for legal challenges. We understand the unique needs of legal projects – speed, effective communication, reliability and confidentiality.

Medical Device & Diagnostics

From initial concept and prototypes to verification/validation, submission and launch, EAG Laboratories is your partner in medical device development. From implant…

From initial concept and prototypes to verification/validation, submission and launch, EAG Laboratories is your partner in medical device development. From implant biocompatibility studies to surface chemistry for contact lenses, we have the experience and techniques to characterize, test and assure purity of medical devices and their materials, components, products and packaging. By utilizing our unique expertise in materials sciences, chemistry, electronics and regulatory support, EAG empowers device companies to create new ways to heal and improve patient quality of life.

Pharmaceuticals

Overcome R&D roadblocks with technical and regulatory know-how. For over two decades, EAG scientists have helped solve complex issues for the pharmaceutical Industry. Using…

Overcome R&D roadblocks with technical and regulatory know-how. For over two decades, EAG scientists have helped solve complex issues for the pharmaceutical Industry. Using multidisciplinary science and engineering, we help improve product development efficiency, avoid regulatory setbacks and uncover sources of problematic manufacturing issues. From GLP and cGMP studies to contaminant and packaging investigations, the scientists of EAG support every phase of the product lifecycle.

Technology

For the high-tech industry, EAG is the leader in materials characterization, surface analysis, microscopy and electronics testing. Our scientists and engineers troubleshoot and…

For the high-tech industry, EAG is the leader in materials characterization, surface analysis, microscopy and electronics testing. Our scientists and engineers troubleshoot and solve issues with consumer electronics, chip packages, printed circuit boards, displays, sensors, high-speed communications and more. We meet the demanding needs of technology innovation, enabling our clients to have confidence in their research & development, supply chains, and ultimately their manufacturing processes

Services

Materials Testing & Analysis

When it comes to understanding the physical structure, chemical properties and composition of materials, no scientific services company offers the breadth of experience, diversity…

When it comes to understanding the physical structure, chemical properties and composition of materials, no scientific services company offers the breadth of experience, diversity of analytical techniques or technical ingenuity of EAG. From polymers to composites, thin films to superalloys—we know how to leverage materials sciences to gain a competitive edge. At EAG, we don’t just perform testing, we drive commercial success—through thoughtfully designed investigations, technically superior analyses and expert interpretation of data.

Microelectronics Test & Engineering

Whether connecting the internet of things, guiding surgical lasers or powering the latest smart phone, integrated circuits and microelectronics touch nearly every aspect of human…

Whether connecting the internet of things, guiding surgical lasers or powering the latest smart phone, integrated circuits and microelectronics touch nearly every aspect of human life. In the world of technology, innovation and continuous improvement are imperatives—and being able to quickly and reliably test, debug, diagnose failures and take corrective action can make the difference between a doomed product launch and building a successful global brand. EAG offers you the world’s largest and most diverse collection of specialized analytical instrumentation, capacity to perform a variety of microelectronic tests in parallel, and the multi-disciplinary expertise required to draw true insight from data.

Litigation Support & Expert Testimony

When you need solid science and investigative engineering to address product failures, inform legal strategy, protect intellectual property or address product liability disputes,…

When you need solid science and investigative engineering to address product failures, inform legal strategy, protect intellectual property or address product liability disputes, turn to EAG. We’ve provided technical consulting, analysis and expert testimony for hundreds of cases involving the aerospace, transportation, medical device, electronics, industrial and consumer product industries. Our team of experts understands the legal process and your need for responsiveness, effective communication, scientifically defensible opinion and confidentiality. From professional consulting to data review to trial preparation and expert witness testimony, ask EAG.

Pharmaceutical & Biopharmaceutical Development Services

EAG Laboratories’ pharmaceutical development services group is now part of Eurofins Biopharma Product Testing. Eurofins BioPharma Product Testing offers…

EAG Laboratories’ pharmaceutical development services group is now part of Eurofins Biopharma Product Testing.

Eurofins BioPharma Product Testing offers unprecedented, multi-location capacity and unmatched expertise through the largest harmonized network of bio/pharma product testing laboratories worldwide. From performing IND-enabling studies to full CMC analytical and QC support, we join your R&D team as a true partner, providing expert guidance to balance regulatory expectations with expediency and cost, and approach technical challenges with flexibility and resolve.

Environmental Testing & Regulatory Compliance

Having helped develop the test methods that shape current regulatory guidelines, EAG chemists, biologists and toxicologists have evaluated the environmental impact of thousands of…

Having helped develop the test methods that shape current regulatory guidelines, EAG chemists, biologists and toxicologists have evaluated the environmental impact of thousands of active ingredients and formulations—from pesticides and pharmaceuticals to industrial chemicals and consumer products. Whether you are exploring “what if” scenarios, registering a new active ingredient or formulation, responding to a data call-in or seeking to understand the latest guidance, turn to EAG for technical excellence, sound advice, GLP-compliant study execution and expert interpretation.

Crop Biotechnology & Development

EAG combines biotechnology and protein characterization expertise with more than 50 years' experience analyzing chemical compounds in plant and environmental matrices to address…

EAG combines biotechnology and protein characterization expertise with more than 50 years’ experience analyzing chemical compounds in plant and environmental matrices to address the growing needs of the biotechnology crop industry. We offer a wide range of techniques required to fully characterize the event insertion and expressed proteins, as well as the various studies required to confirm the food, feed and environmental safety of products that represent the trait. From early-stage protein confirmation to GLP-compliant EDSP and allergenicity testing, we help you make faster, more informed development decisions and comply with evolving global regulations of genetically engineered crops.

Custom Synthesis & Radiolabeling

No contract service provider has more experience performing custom synthesis and producing isotopically labeled compounds to support product development in life science, chemical…

No contract service provider has more experience performing custom synthesis and producing isotopically labeled compounds to support product development in life science, chemical and related industries than we do. From 14C and 3H radiolabeled clinical trial materials synthesized under cGMP, to stable-labeled active ingredients for metabolism and environmental fate/effects testing, turn to EAG. We have extensive experience with multi-step and other complex synthesis projects, and our comprehensive, in-house analytical services ensure quick turnaround of purity and structural confirmation.

Techniques

Chromatography

Using an array of advanced separation techniques and innovative technology, we conduct highly precise analytical chromatography for various industries. Whether you want a closer…

Using an array of advanced separation techniques and innovative technology, we conduct highly precise analytical chromatography for various industries. Whether you want a closer look at the purity of your pharmaceutical or need to better understand an agrochemical’s components, EAG has the expertise to separate and evaluate any compound.

Mass Spectrometry

Need to evaluate the molecular structure of a compound or identify its origins? EAG knows how. With state-of-the-art tools, we can separate, vaporize and ionize the atoms and…

Need to evaluate the molecular structure of a compound or identify its origins? EAG knows how. With state-of-the-art tools, we can separate, vaporize and ionize the atoms and molecules in almost any pure or complex material to detect and obtain mass spectra of the components. We rely on decades of experience in mass spectrometry to provide our clients with precise analyses and the best detection limits.

Imaging

EAG is a world leader in high-resolution imaging down to the atomic level. We offer unmatched analytical know-how, generating extremely detailed surface and near surface images…

EAG is a world leader in high-resolution imaging down to the atomic level. We offer unmatched analytical know-how, generating extremely detailed surface and near surface images for various industries, from consumer electronics to nanotechnology. Using state-of-the-art equipment and innovative techniques, we conduct expert imaging to aid in failure analysis, dimensional analysis, process characterization, particle identification and more. If you want to investigate a material with angstrom scale resolution, you can count on EAG to get the job done quickly and precisely.

Spectroscopy

EAG offers a vast array of spectroscopic techniques to clients in various industries, from defense contractors to technology pioneers. We combine unparalleled expertise and…

EAG offers a vast array of spectroscopic techniques to clients in various industries, from defense contractors to technology pioneers. We combine unparalleled expertise and methodology with cutting-edge technology to analyze your organic, inorganic, metallic and composite materials for identification, compositional, structural and contaminant information. Whether you need expert spectroscopic analysis to improve your production process or to surmount a technical challenge, EAG is up to the task.

Physical/Chemical Characterization

Need to identify your unique material? Want to analyze the thermal properties of a sample, or measure the success of a process step? If it has to be done quickly and it has to be…

Need to identify your unique material? Want to analyze the thermal properties of a sample, or measure the success of a process step? If it has to be done quickly and it has to be done right, you can count on EAG. We offer a range of adaptable techniques and innovative methods to evaluate the physical and chemical characteristics of any compound. Our highly precise testing and analytical services will improve your production process, expedite R&D and help you conquer any technical challenge.

About

A Global Scientific Services Company

One of the most respected names in contract research and testing, EAG Laboratories is a global scientific services company operating at the intersection of science, technology and…

One of the most respected names in contract research and testing, EAG Laboratories is a global scientific services company operating at the intersection of science, technology and business. The scientists and engineers of EAG apply multi-disciplinary expertise, advanced analytical techniques and “we know how” resolve to answer complex questions that drive commerce around the world.

Our Customers

Science and technology transcend industry boundaries, and so does demand for EAG’s expertise. We partner with companies across a broad spectrum of high-tech, high-impact and…

Science and technology transcend industry boundaries, and so does demand for EAG’s expertise. We partner with companies across a broad spectrum of high-tech, high-impact and highly regulated industries. We help our customers innovate new and improved products, investigate manufacturing problems, perform advanced analyses to determine safety, efficacy and regulatory compliance, and protect their brands.

Our Company Culture

EAG’s corporate culture is firmly rooted in four guiding principles: “foster a growth mindset,” “find a better way,” “earn more loyal customers,” and “win…

EAG’s corporate culture is firmly rooted in four guiding principles: “foster a growth mindset,” “find a better way,” “earn more loyal customers,” and “win together.” Across all of our 20+ locations, you will find a true passion for science and the power of science to improve the world we live in. Hear what some of our ~1200 scientists, engineers and support personnel say about what it means to be part of EAG Laboratories.

Careers

EAG is growing, and we are always looking for talented, problem-solving oriented individuals to join our company. If you have a “we know how” spirit, we want to hear from you.…

EAG is growing, and we are always looking for talented, problem-solving oriented individuals to join our company. If you have a “we know how” spirit, we want to hear from you. Browse current openings now, and re-visit our careers page often.

Direct Chemical Analysis of Ceramic Matrix Composites

WHITE PAPER

Karol Putyera, Chris Iversen, Xinwei Wang and Rajiv S. Soman1

ABSTRACT

Ceramic matrix composites (CMCs) are the next generation of aerospace materials. Similar to practically any material used by the aerospace industry, controlling the purity of “aerospace grade” composites is going to be indispensable to achieve the desirable mechanical properties, reliability and lifetime. On the analytical side, CMCs present multiple challenges for conventional chemical analysis techniques. The extreme chemical inertness of CMCs toward common digestion media, for instance, makes the use of solution-based chemical analysis techniques for purity control exceedingly challenging. Although direct solid sampling techniques can eliminate the necessity of sample digestion, the complex nature of ceramic matrix composites could still cause large measurement uncertainties.

Fast-flow glow discharge mass spectrometry (FF-GDMS) is a direct solid sampling analytical technique designed for high sensitivity, full survey elemental analysis of solids. Operating the fast-flow source in pulse modes permits better control of the atomization of complex samples enabling mass fraction distribution of elements to be monitored in favorably adjustable volume fractions. In this study, we demonstrate that this technique is exceptionally robust and one of the most sensitive analytical tools currently available for full survey chemical analyses as well as depth specific distribution analysis of CMC materials. Due to the complexity of CMC samples from plasma sputtering point of view, in addition to FF-GDMS measurements, we also investigated complementary characterization techniques, such as direct insertion probe mass spectrometry (DIP-MS), inert gas fusion – infrared/thermal conductivity analysis (IGA), and high resolution thermogravimetric analysis (HR-TGA), for evaluation and/or verification of gas forming elements present in CMC samples.

INTRODUCTION

CMCs adopt the common reinforcement/matrix architecture. The inherent anisotropy in structure calls for controlling not only the bulk level of impurities but also their distributions. Low atomic mass elements such as B, C, N, O, Al and Si present in CMCs could outgas fairly easily during the manufacturing processes and during their service phases as compared to traditional alloys, resulting in internal voids, erosion and even corrosion of components. Hence, it is envisioned that chemical impurities and distribution, as well as outgassing, must be thoroughly understood and controlled to realize the full potential of CMC materials.

CMCs present unique challenges to conventional chemical analysis techniques. They show chemical inertness toward even the most aggressive digestion media, rendering wet chemistry-based analysis techniques ineffective, let alone not appealing due to loss of spatial distribution information.2 In that sense, direct solid sampling techniques, which eliminate the need of sample digestion altogether and have the ability to provide depth-specific distribution information, are gaining attraction. However, the complex nature of CMCs could lead to large measurement uncertainties, especially for those direct solid sampling techniques which require matrix-matched calibration standards.

Thermo Scientific introduced fast-flow glow discharge mass spectrometry technique, in their Element GD model, in 2005. This instrument combines a fast flow direct current GD (Glow Discharge) source with a sector field mass analyzer. One of the main features of the Element GD is that it has very efficient direct solid sampling capability, fast data acquisition, and very high mass resolution (up to 10,000). Figure 1 illustrates the schematic of the fast flow GD source. In this configuration, a discharge gas flow, typically argon, is directed toward the sample surface via a vertically aligned replaceable flow tube. At discharge gas flow rates of few hundreds of sccm/min, the sample surface sputters at very high atomization rates (μm/min) setting the prerequisites for very sensitive mass fraction determinations.3 The presently investigated GD source differs from those employed in VG9000 and Astrum GDMS models. The fast flowing gas generates a jet stream that moves in the direction of the plasma region from the cathode surface. This jet stream-assisted transport of the sputtered atoms, among other effects, noticeably makes sputtering more uniform for samples having internal voids, cavities or rough surfaces, such as composites. This enhancement becomes even more pronounced when the FF-GD source voltage is modulated.4

Figure 1: Schematic illustration of the fast flow high power source, the standard GD source deployed on the FF-GDMS instruments.

Figure 1: Schematic illustration of the fast flow high power source, the standard GD source deployed on the FF-GDMS instruments.

Previously, we have demonstrated FF-GDMS as a very effective tool in assessing the trace impurities in isotropic nuclear grade graphite.5 In this study, FF-GDMS was evaluated for its applicability for chemical analysis of carbon fiber–reinforced carbon composites (CFRCs). Our findings demonstrate the advantages of this method for analysis of composite samples with complex architectures, especially when the source is operated in modulated mode. Our approach is very effective for full survey chemical analysis of composites, providing sensitivities down to ultra-trace levels practically for all elements in the periodic table. The technique has also shown to be extremely robust, making it ideal for daily quality or process control of a broad range of materials that are presently actively sought for advanced applications. In addition to full survey analysis of CFRC samples by FF-GDMS, we have examined the release characteristics of gas-forming elements in CFRCs. Outgassing analysis, important in its own right as a quality gauge to CFRC, also helps to validate GDMS measurements, given that outgassing molecular species in the plasma can affect the atomization and ionization processes. Hence, multiple complementary analytical approaches were studied for evaluations of gas forming elements in CFRCs.

EXPERIMENTATION

GDMS Sample Preparation

Figure 2 shows the Scanning Electron Microscopy (SEM) images of a CFRC sample (grade PC70: chopped fiber, reinforcement pattern 12K Twill). Typical of fiber-reinforced composites, it is characterized with surface roughness, and cavities formed by the fiber pattern, and with micro particle impurities dispersed therein. This is not a flat sample geometry that is typically analyzed by FF-GDMS. In this study, a square size testing specimen (20 mm × 20 mm × 1 mm) was cut out from a large CFRC plate and directly mounted onto the GD Source. No further surface pre-treatment was performed. For bulk impurity measurement, potential surface contaminants were pre-sputtered before equilibrated readings were acquired through a representative sampling volume for statistical evaluation.

Figure 2: SEM images on carbon fiber-reinforced carbon composite material, grade PC70 (Schunk Carbon Technology), in COMPO mode (mostly z-contrast). The bright spots (shown circled above) are micron size surface impurities having densities higher than that of carbon.

Figure 2: SEM images on carbon fiber-reinforced carbon composite material, grade PC70 (Schunk Carbon Technology), in COMPO mode (mostly z-contrast). The bright spots (shown circled above) are micron size surface impurities having densities higher than that of carbon.

Method Development

The optimum nominal discharge gas settings, isotopes and measurement modes were investigated to adjust for sensitivities and atomization rates. Figure 3 highlights the impact of argon gas flow rate on plasma ignition and the subsequent atomization rate (ic – carbon ion current in Ampere). In the DC mode, plasma is barely ignited (ic ≈ 0 A) below 400 sccm/min argon flow; in comparison, glow discharge is readily established at similar flow rate when operated in the pulse mode, with ic ≈ 6E-11A. Further, the pulsed operation is shown to significantly increase the carbon ion intensity throughout the entire used gas flow rate range (400 – 540 sccm/min). At a flow rate of ≈ 455 sccm/min, for example, ic increases from 2.5E-11 A to 1.15E-10 A, a nearly five-fold increase. The argon background signal remains fairly constant in the pulse mode; whereas, in the DC mode, the argon signal increases with increasing argon flow rates. Thus, it is apparent that the pulse-mode operation can significantly improve the signal intensity/noise ratio, leading to more sensitive detection of trace and ultratrace elements.

Figure 3: Effect of nominal discharge gas flow rates on carbon ion intensity and argon background in both direct current (DC) and pulsed (2 kHz, 50 μs) modes.

Figure 3: Effect of nominal discharge gas flow rates on carbon ion intensity and argon background in both direct current (DC) and pulsed (2 kHz, 50 μs) modes.

Figure 4: Medium resolution scan (R=4000) of 48Ti+ and 56Fe+ trace elements. Polyatomic interferences from 36Ar12C+ and 40Ar16O+ are well resolved.

Figure 4: Medium resolution scan (R=4000) of 48Ti+ and 56Fe+ trace elements. Polyatomic interferences from 36Ar12C+ and 40Ar16O+ are well resolved.

Generally, medium resolution mode appears to be adequate for routine survey measurements of CFRC composites. Figure 4 illustrates, as an example, how isobaric interferences can be resolved from analyte peaks of Ti and Fe, respectively, in a medium mass resolution mode.

One important aspect in method development is to evaluate the mass fraction equilibration time. This was accomplished by monitoring mass fraction development over sputtering time. In this investigation, the carbon matrix signal reached stable readings in a matter of several minutes after initiating data acquisition. However, operating in the DC mode, it takes at least 30 minutes of plasma sputtering time for some analytes to reach equilibrium state. Local turbulent flow created by the uneven sample surface and the presence of particulates on the surface and within interior voids, is suspected to be largely responsible for the longer equilibration time.

Figure 5: Trace impurity concentration profiles vs sputtering time for some common impurity elements found in CFRCs by pulsed GD acquisition. Average sputtering speed is ≈ 0.1 μm/min for carbonaceous materials. Concentration of most impuri-ties levels off within ≈ 10 min of sputtering, corresponding to an estimated sampling depth of ≈ 1 μm.

Figure 5: Trace impurity concentration profiles vs sputtering time for some common impurity elements found in CFRCs by pulsed GD acquisition. Average sputtering speed is ≈ 0.1 μm/min for carbonaceous materials. Concentration of most impuri-ties levels off within ≈ 10 min of sputtering, corresponding to an estimated sampling depth of ≈ 1 μm.

However, the equilibration time can be substantially shortened in the pulse mode. Figure 5 illustrates the temporal profiles of some commonly encountered trace impurities in CFRCs. The concentration ranges from ng/g to mg/g levels. Most elements were found leveling off within 10 min of sputtering. It is reasoned that during the DC operation, the back pressure created by continuous incoming argon flux from the plasma toward the sample localizes impurity atoms present within partially exposed voids or apertures. In the pulsed operation, such back pressure disappears during the pulse off period, creating a pressure wave which effectively sweeps impurities out of voids and cavities before next pulse arrives.

Instrumental Settings

Since pulsed modes provided significantly higher matrix ion signal intensities and need shorter equilibration times, all survey measurements in this study were conducted using the following instrumental parameters:

  • Operation mode: voltage modulated at pulse frequency 2 kHz, pulse on 50 μs and off 450 μs in each duty cycle
  • Discharge current: 5.5 mA
  • Discharge voltage: 1120 v
  • Discharge gas: 440 sccm/min Ar
  • Matrix signal intensity: ≈ E10 cps (Medium Resolution)
  • Consumables: graphite anode cap diameter Φ ≈ 8 mm; flow tube length L ≈ 20 mm
RESULTS

Bulk chemical survey analysis

All results presented here were measured as ion beam ratios and adjusted to mass fraction results by applying element specific sensitivity factors from the instrument’s Standard RSF table (Table 1). This is quite often a common practice for initial quantification of experimental results or for analyses without certified reference materials. With this generalized approach the nominal results are typically within a factor or two of accepted values.

Table 1: Equilibrated mass fraction results of elements, which were found to be present in PC70 above the method determination limits.

Table 1: Equilibrated mass fraction results of elements, which were found to be present in PC70 above the method determination limits.

Sensitivity

Typically the detection limit values achieved are at ultra-trace levels, and are limited only by the signal to noise ratio of approximately few counts per second (cps) vs. 1E10 cps (background noise versus Carbon signal integrated intensity). Elements that yield higher detection limit values are either due to lower isotopic abundances of the isotopes, such as 44Ca, 82Se, or are in the vicinity of the suitable isotopes where the background noise is higher due to the presence of interfering isobaric peak signals.

Outgassing assessment of CFRCs

Outgassing from sample destabilizes the plasma during GDMS analysis. Substantial outgassing can make the sample analysis impossible to accomplish. Furthermore, outgassing of CFRCs is an important issue that needs to be dealt with from materials engineering point of view, whether in processing or during the service period. In this study, outgassing of CFRCs was investigated over a broad range of temperature and pressure regimes.

Figure 6: High resolution TGA evaluation of trace outgassing of C/C composite. Total outgassing amount was determined for each temperature stage.

Figure 6: High resolution TGA evaluation of trace outgassing of C/C composite. Total outgassing amount was determined for each temperature stage.

Thermogravimetric analysis measures the mass loss as a function of temperature and time, providing sensitive measurement of outgassing rate and total outgassing levels. Figure 6 shows the TGA profile of CFRCs in inert atmosphere from room temperature to 1000ºC. Using a sample mass of ≈100 mg, one can detect 100 μg/g (i.e. 0.01%) mass loss with this approach. In this case, the sample exhibits two-stage mass loss, at 800 μg/g and 200 μg/g by 500ºC and 1000 ºC respectively.

Figure 7: Schematic diagram of DIP-MS sampling configuration.

Figure 7: Schematic diagram of DIP-MS sampling configuration.

Figure 8: Outgassing profiles of carbon composites upon heating, as acquired by DIP-MS technique. Temperature program: ramp to 500°C at 100°C/min and hold at 500°C for 3 min.

Figure 8: Outgassing profiles of carbon composites upon heating, as acquired by DIP-MS technique. Temperature program: ramp to 500°C at 100°C/min and hold at 500°C for 3 min.

One of the major challenges in outgassing analysis is loss of analytes from the source to the detector, in particular when less volatile or highly reactive outgassing species are formed. Incorporating a heated transfer line is a solution exhibiting limited success. Here we propose a vacuum outgassing analysis technique DIP-MS. Figure 7 illustrates the sample introduction component of DIP-MS. A quartz sample vial is mounted on the tip of a temperature programmed probe, and is directly exposed to the high vacuum environment (≈ 10-7 torr) of the mass analyzer source. Equipped with this sample introduction system and a quadrupole mass analyzer capable of scanning masses of up to 1000 amu, DIP-MS is extremely effective in survey analysis of outgassing molecular species, including those with high reactivity or low volatility. In a DIP-MS analysis, typically a small amount of sample (1 ≈ 10 mg) is evaluated. Figure 8 illustrates the identified main outgassing species and their temperature/time-dependent releasing profiles, including CO2, C2F4, SO2, hydrocarbons and fluorocarbons. These results clearly demonstrate that DIP-MS is a very powerful tool for identifying and acquiring outgassing profiles, in particular for evaluating materials for vacuum or low pressure application. However, the technique is limited to qualitative analysis at this point, although semi-quantitative comparative analysis is possible when one uses similar sample size. Another limitation was temperature capability. The standard DIP-MS operates from room temperature to 450°C. As a result, a high-temperature model (up to 1500°C) was developed, making it ideal for outgassing study of CMCs.

Figure 9: CO and CO2 outgassing profiles of C/C composites acquired with inert gas fusion – infrared technique in stepped temperature mode. Degree of deoxygenation in each temperature regime was quantified, corresponding to different oxygen chemistries in the composite.

Figure 9: CO and CO2 outgassing profiles of C/C composites acquired with inert gas fusion – infrared technique in stepped temperature mode. Degree of deoxygenation in each temperature regime was quantified, corresponding to different oxygen chemistries in the composite.

To acquire outgassing information at very high temperature (up to 2000 ºC), inert gas fusion technique has been evaluated. This technique is commonly used in the steel industry to quantify the trace elements such as O, N and H, but is sought here for high temperature outgassing analysis of CFRCs, since these elements can bind readily with matrix carbon atoms forming volatile species. Figure 9 illustrates the outgassing profiles of CO and CO2, two main oxygen-containing outgassing species from CFRCs, up to 2000°C. In the ramped temperature mode, CO and CO2 released in each temperature regime reveal various oxygen chemistries in CFRCs, and provide guideline for deoxygenation of these composites. Using NIST traceable oxygen standards, quantification of oxygen content can be readily achieved, even at μg/g level.

Table 2: C, H, O and N content of CFRCs

Table 2: C, H, O and N content of CFRCs*

For determining total amount of outgassing elements O, N and H, one can take advantage of the well-established ASTM methods, incorporating inert gas fusion – infrared and thermal conductivity detection approaches, using NIST traceable standards for calibration. Table 2 summarizes the measured C, O, N and H content of this CFRC sample. The typical precision values for trace level H, O, and N are 4, 10, and 12% RSD (n=3-5) respectively. It is worth mentioning that with such tight RSD values, one can use the H/C ratio to evaluate the average aromatic cluster size in CFRCs.6 For this particular CFRC, the estimated average aromatic cluster size is slightly greater than 500 × 500 (row of benzene rings × column of benzene rings) per graphene sheet.

CONCLUSION

Direct chemical analysis of CMCs is a challenging task. In this study, we demonstrated the robustness of FF-GDMS when conducting a full survey chemical analysis of CFRCs. The technique provides rapid assessment of nearly all elements in the periodic table, without the need for complex sample preparation. When operated in the pulsed mode, it also allows one to acquire surface contaminant information. In addition, we also assessed the analytical capability for outgassing behaviors of CFRCs in various temperature and pressure regimes, from room temperature up to 2000°C and ambient pressure to 10-7 torr, using multiple analytical tools, including DIP-MS, TGA and inert gas fusion – IR/TCD in stepped temperature mode.

REFERENCES
  1. Putyera, Karol, et al., “Direct Chemical Analysis of Ceramic Matrix Composites.” SAMPE Conference Proceedings. Seattle, WA, May 22-25, 2017. Society for the Advancement of Material and Process Engineering – North America, 2017, 278 – 287.
  2. Manna, S., et al., “Digestion Methods for Advanced Ceramic Materials and Subsequent Determination of Silicon and Boron by Inductively Coupled Plasma Atomic Emission Spectrometry.” J. Anal. At. Spectrom., 1997, 12, 975 – 979.
  3. Prohaska, Thomas, et al. Sector Field Mass Spectometry for Elemental and Isotopic Analysis. London : Royal Society of Chemistry, 2014.
  4. Churchill, Glyn, et al. “New μs-pulsed DC glow discharge assembly on a fast flow high power source.” J. Anal. At. Spectrom., 2011, 26, 2263.
  5. Wang, Xinwei, et al. Quantification of Trace and Ultra-trace Elements in Nuclear Grade Manufactured Graphites by Fast-Flow Glow Discharge Mass Spectrometry and by Inductively Coupled Plasma – Mass Spectrometry after Microwave – Induced Combustion Digestions. MRS Proceedings, 2010, 1215. doi: 10.1557/PROC-1215-v16-09.
  6. Xiao, Xin, et al. H/C atomic ratio as a smart linkage between pyrolytic temperatures, aromatic clusters and sorption properties of biochars derived from diverse precursory materials. Scientific Reports, 2014, 22644.

To enable certain features and improve your experience with us, this site stores cookies on your computer. Please click Continue to provide your authorization and permanently remove this message.

To find out more, please see our privacy policy.