Sample Tube Research Articles

Determination of triacetone triperoxide (TATP) traces using passive samplers in combination with GC-MS and GC-PCI-MS/MS methods

The use of organic peroxides for the preparation of homemade explosives (HMEs) is common among terrorists due to inexpensive precursor chemicals and simple synthetic procedures. Triacetone triperoxide (TATP) is the most notable peroxide explosive, and has been deployed in several terrorist attacks as explosive filling of improvised explosive devices (IEDs). Forensic identification of TATP in pre-blast and post-blast residues, including on-site analysis, poses significant analytical challenges and induces demand for practicable and sensitive detection techniques. This work presents a concept suitable for laboratory and on-site identification of TATP residues in liquid samples (aqueous TATP synthetic waste) and in gas phase. It is based on TATP enrichment from the aqueous or gas phase using different types of passive samplers (polydimethylsiloxane (PDMS) sampling rods and activated carbon sampling tubes (ACST)) and subsequent identification of the explosive by gas chromatography-mass spectrometry (GC-MS) or GC with positive chemical ionization and tandem MS (GC-PCI-MS/MS) analytical techniques. Additionally, investigation of the stability of TATP in aqueous solutions and of the stability of enriched TATP in passive samplers under different storage conditions, as well as development of TATP re-extraction procedures from passive samplers have been performed in this study. The practical use of passive samplers was demonstrated during and after TATP production processes. Moreover, post-blast sampling of TATP under different conditions of controlled blasting events was investigated using the passive sampling concept.

Preanalytical temperature and storage stability of specific IgE antibodies in serum

Allergen-specific serum immunoglobulin E (sIgE) levels are a cornerstone in allergy diagnostics. While immunoglobulins are known to be relatively stable molecules, the influence of preanalytical factors on the stability of sIgE is not thoroughly investigated. We studied the effect of several preanalytical factors: (1) delayed centrifugation of serum samples in tubes with separating gel for 10, 24 and 48 h, (2) prolonged storage at 5 °C for 3, 7, 10 and 14 days, (3) storage tube type (primary tube with separating gel or secondary tube), (4) repeated freeze-thawing cycles, and (5) prolonged storage at −20 °C for 4 and 8 weeks. We found that sIgE is stable at room temperature for 48 h before centrifugation and for 10 days at 5 °C after centrifugation. There was no effect of the separating gel after storing serum for 1 week in the freezer. However, storage for 4–8 weeks, and introducing more than one freeze-thaw cycle resulted in a larger variation of sIgE levels. In conclusion, we found that sIgEs are stable under various preanalytical conditions, which allows for flexible handling of samples for a comprehensive portfolio of sIgE analyses.

Uptake of Per- and Polyfluoroalkyl Substances by Fish, Mussel, and Passive Samplers in Mobile-Laboratory Exposures Using Groundwater from a Contamination Plume at a Historical Fire Training Area, Cape Cod, Massachusetts.

Aqueous film-forming foams historically were used during fire training activities on Joint Base Cape Cod, Massachusetts, and created an extensive per- and polyfluoroalkyl substances (PFAS) groundwater contamination plume. The potential for PFAS bioconcentration from exposure to the contaminated groundwater, which discharges to surface water bodies, was assessed with mobile-laboratory experiments using groundwater from the contamination plume and a nearby reference location. The on-site continuous-flow 21-day exposures used male and female fathead minnows, freshwater mussels, polar organic chemical integrative samplers (POCIS), and polyethylene tube samplers (PETS) to evaluate biotic and abiotic uptake. The composition of the PFAS-contaminated groundwater was complex and 9 PFAS were detected in the reference groundwater and 17 PFAS were detected in the contaminated groundwater. The summed PFAS concentrations ranged from 120 to 140 ng L-1 in reference groundwater and 6100 to 15,000 ng L-1 in contaminated groundwater. Biotic concentration factors (CFb) for individual PFAS were species, sex, source, and compound-specific and ranged from 2.9 to 1000 L kg-1 in whole-body male fish exposed to contaminated groundwater for 21 days. The fish and mussel CFb generally increased with increasing fluorocarbon chain length and were greater for sulfonates than for carboxylates. The exception was perfluorohexane sulfonate, which deviated from the linear trend and had a 10-fold difference in CFb between sites, possibly because of biotransformation of precursors such as perfluorohexane sulfonamide. Uptake for most PFAS in male fish was linear over time, whereas female fish had bilinear uptake indicated by an initial increase in tissue concentrations followed by a decrease. Uptake of PFAS was less for mussels (maximum CFb = 200) than for fish, and mussel uptake of most PFAS also was bilinear. Although abiotic concentration factors were greater than CFb, and values for POCIS were greater than for PETS, passive samplers were useful for assessing PFAS that potentially bioconcentrate in fish but are present at concentrations below method quantitation limits in water. Passive samplers also accumulate short-chain PFAS that are not bioconcentrated.

FE micromodel of a cord-rubber composite tube sample subjected to uniaxial tension

The aim of this study is to examine displacements, strains and stresses of a railway composite cord-rubber air brake tube undergoing uniaxial tension by microscale modelling. The micromodel is based on the macromodels (by matching the boundary conditions of the micromodels with displacements of the macromodels) created previously by authors of this article. The reinforcing yarns are described by an orthotropic, elastic material model, whereas the matrix has been described by a 2 parameter Mooney-Rivlin model, which all have been validated before by a uniaxial tensile test and a three-point bending test. Force-displacement curves of the micromodel and experimental results show a considerably good agreement. Failure of the reinforcement layers does not occur in case of the uniaxial tension of the composite tube sample, there was no failure event observed during the experiment of the tube sample. Load transfer mechanism has been demonstrated and characterized numerically by strain and stress results inside and between reinforcement layers (implying shear plays a dominant role in the load-transfer mechanism). The microscale nature of the FE model ensures that the strain and stress results are representative for the reinforcement layers.

Heterologous Vector—mRNA Based SARS-CoV-2 Vaccination Strategy Appears Superior to a Homologous Vector—Based Vaccination Scheme in German Healthcare Workers Regarding Humoral SARS-CoV-2 Response Indicating a High Boosting Effect by mRNA Vaccines

Longitudinal humoral SARS-CoV-2 (severe acute respiratory syndrome coronavirus type 2) immunity for up to 15 months due to vaccination, the efficacy of vaccination strategies (homologous, vector-vector versus heterologous, vector-mRNA), the influence of vaccination side effects, and the infection rate in German healthcare workers need to be investigated. In this study, 103 individuals vaccinated against SARS-CoV-2 were enrolled to examine their anti-SARS-CoV-2 anti-N- and anti-RBD/S1-Ig levels. A total of 415 blood samples in lithium heparin tubes were prospectively obtained, and a structured survey regarding medical history, type of vaccine, and vaccination reactions was conducted. All participants demonstrated a humoral immune response, among whom no values decreased below the positivity cutoff. Five to six months after the third vaccination, three participants showed anti-RBD/S1 antibodies of less than 1000 U/mL. We observed higher levels for heterologous mRNA-/vector-based combinations compared to pure vector-based vaccination after the second vaccination, which is harmonized after a third vaccination with the mRNA-vaccine only in both cohorts. The incidence of vaccine breakthrough in a highly exposed cohort was 60.3%. Sustained long-term humoral immunity was observed, indicating the superiority of a heterologous mRNA-/vector-based combination compared to pure vector-based vaccination. There was longevity of anti-RBD/S1 antibodies of at least 4 and up to 7 months without external stimulus. Regarding vaccination reactogenity, the occurrence of local symptoms as pain at the injection site was increased after the first mRNA application compared to the vector-vector cohort with a general decrease in adverse events at later vaccination time points. Overall, a correlation between the humoral vaccination response and vaccination side effects was not observed. Despite the high prevalence of vaccine breakthroughs, these only occurred in the later course of the study when more infectious variants, which are, however, associated with milder courses, were present. These results provide insights into vaccine-related serologic responses, and the study should be expanded using additional vaccine doses and novel variants in the future.

Indoor and outdoor air quality assessment in daycare centres in Ghent (Belgium) in view of outdoor sleeping in an urban environment

Within Flanders, there is an increasing trend to let children sleep outdoors while in daycare. However, within an urban environment, the densely spread emission sources might affect the air quality and possibly limit the areas where outdoor sleeping is favourable. Nevertheless, there is a lack of data regarding the atmospheric pollution levels in and around daycare centres (DCC). Therefore, the focus of this study is to chemically characterize the air quality indoors, outdoors, and in specifically designed cubicles for outdoor sleeping at 12 DCCs spread over the city of Ghent (Belgium). The measuring of a very broad range of different pollutants, provides unique data for indoor and outdoor air quality at daycare centres in Ghent. The use of axial tube (for volatile organic compounds, VOCs) and Radiello (for NO2, SO2, O3) passive samplers enables multi-component sampling, resulting in time-weighted average concentrations for one week. Forty-seven VOCs are identified and, for the majority (40), indoor to outdoor concentration (I/O) ratios higher than one are found. For the remaining seven compounds (e.g. benzene) outdoor concentrations are a factor 1.3–17.9 (median) higher than indoors. Median indoor TVOC concentrations are 152 μg/m3 and 142 μg/m3 for the September and January campaign, respectively. Outdoors, these median TVOC concentrations are much lower (24.5 μg/m3 and 30.6 μg/m3). For NO2, no noticeable differences are observed between average indoor and outdoor concentrations (indoors 12 ± 3 μg/m3 and 13 ± 2 μg/m3 for the September and January campaign, respectively, and outdoors 11 ± 3 μg/m3 and 14 ± 4 μg/m3). The highest (outdoor) measured concentration is 21 ± 1 μg/m3. SO2 concentrations are below 2.62 μg/m3 (LOQ). Average indoor O3 concentrations are 4 ± 3 μg/m3 and 2 ± 2 μg/m3 for the September and January campaign, respectively. Much higher values are measured outdoors (46 ± 3 μg/m3 and 40 ± 11 μg/m3), but the concentrations stayed well below legal standards.

RIDA®GENE Helicobacter pylori PCR on the ELITe InGenius System

PCR detection of Helicobacter pylori infection in gastric biopsies allows the detection of this bacterium and the mutations associated with macrolide resistance. The aim of this study was to evaluate the performance of RIDA®GENE H. pylori PCR (r-Biopharm) on the ELITe InGenius System (Elitech). Two hundred gastric biopsies were obtained. These biopsies were ground in nutrient broth. Two hundred microliters of this suspension was treated with proteinase K, and then, 200 µL was transferred to an ELITe InGenius sample tube and tested using RIDA®GENE H. pylori PCR reagents. In-house H. pylori PCR was used as a reference. The sensitivity of RIDA®GENE H. pylori PCR with ELITe InGenius was 100%, the specificity was 98% (95% confidence interval (CI), 95.3–100%), the PPV was 98% (95% CI, 95.3–100%), and the NPV was 100% for the detection of H. pylori. All of these parameters were 100% for the categorization of macrolide resistance. The adaptation of RIDA®GENE H. pylori PCR reagents on the ELITe InGenius System was successful. This PCR is easy to use on this system.

Extraction-free clinical detection of SARS-CoV-2 virus from saline gargle samples using Hamilton STARlet liquid handler

As part of the COVID-19 pandemic, clinical laboratories have been faced with massive increases in testing, resulting in sample collection systems, reagent, and staff shortages. We utilized self-collected saline gargle samples to optimize high throughput SARS-CoV-2 multiplex polymerase chain reaction (PCR) testing in order to minimize cost and technologist time. This was achieved through elimination of nucleic acid extraction and automation of sample handling on a widely available robotic liquid handler, Hamilton STARlet. A customized barcode scanning script for reading the sample ID by the Hamilton STARlet’s software system was developed to allow primary tube sampling. Use of pre-frozen SARS-CoV-2 assay reaction mixtures reduced assay setup time. In both validation and live testing, the assay produced no false positive or false negative results. Of the 1060 samples tested during validation, 3.6% (39/1060) of samples required retesting as they were either single gene positive, had internal control failure or liquid aspiration error. Although the overall turnaround time was only slightly faster in the automated workflow (185 min vs 200 min), there was a 76% reduction in hands-on time, potentially reducing staff fatigue and burnout. This described process from sample self-collection to automated direct PCR testing significantly reduces the total burden on healthcare systems in terms of human resources and reagent requirements.

In-situ combustion technique for developing fractured low permeable oil shale: Experimental evidence for synthetic oil generation and successful propagation of combustion front

The idea of in-situ combustion (ISC) for oil shale development and conversion has been proposed recently. Due to the low permeability of oil shale, it usually requires fracturing operation before air injection. However, one of the biggest technical questions is, whether the combustion front can be established and steadily propagate in the low permeable oil shale with fractures. To date, no experimental work has been reported to support this. The target of this work is to provide experimental evidence to answer this question. We have managed to create a novel method for packing and fracturing oil shale core samples in a combustion tube for simulating ISC processes. A systematic analysis for the physical–chemical modeling of ISC process in combustion tube was performed, including temperature profile, pressure drop buildup, composition of produced gases, X-ray computed tomography (CT) and visual inspection, as well as total organic content analysis of oil shale samples before and after combustion, calculation of combustion parameters (air requirement, air/fuel ratio, apparent atomic H/C ratio, oxygen utilization, and O2/fuel ratio), and synthetic oil production. All results indicated the successful establishment and propagation of the combustion front in the fractured, low-permeability oil shale sample. In addition, the permeability of oil shale was increased 2–3 times during combustion, which can be an important factor that supports the stable propagation of the combustion front. Furthermore, the effect of water and catalysts on ISC performance was investigated. It was found that water promotes the cracking reactions of heavy oils to produce CO2 and hydrocarbon gases, and the co-existence of catalysts and water together further improved the performance of the ISC process and synthetic oil production. The findings in this work provide the experimental evidence of the successful establishment and propagation of combustion front in fractured, low-permeability oil shale, and technically proves the feasibility of using ISC technology for in-situ retorting of oil shale to generate synthetic oil for the development and conversion of low permeable oil shale with additional fracturing.

Pressure-retaining sampler for sediment and overlying seawater based on heavy duty ROV-Jellyfish

Methane leakage at sediment seawater interface is an important basis for gas hydrate exploration. Therefore, a low disturbance in-situ encapsulation and pressure-retaining sampler for sediment and overlying water with a working depth of 3000 m is developed recently to provide support for evaluating regional methane flux. This sampler can also separate and transfer the sediment and overlying water with retaining pressure. By using the coupled Eulerian-Lagrangian (CEL) approach in the finite element software ABAQUS, which provides a variety of soil constitutive models, the tube-soil interaction during penetration is numerically investigated. The use of a 60 mm diameter sampling tube can achieve a higher sampling rate under low penetration resistance. Through the laboratory pressure test (30 MPa), it is verified that the pressure-retaining capacity of sampler can ensure that the pressure drop does not exceed 3.9% within 2 h. Furthermore, the pressure-retaining samples of more than 700 ml were obtained each time in sea trials at three stations, which verifies the feasibility of the device application. The analysis of gas composition shows that the dissolved gas is mainly methane (> 99.1%), and all the sampling points fall in the thermogenic gas area.

Reconversion of Parahydrogen Gas in Surfactant-Coated Glass NMR Tubes.

The application of parahydrogen gas to enhance the magnetic resonance signals of a diversity of chemical species has increased substantially in the last decade. Parahydrogen is prepared by lowering the temperature of hydrogen gas in the presence of a catalyst; this enriches the para spin isomer beyond its normal abundance of 25% at thermal equilibrium. Indeed, parahydrogen fractions that approach unity can be attained at sufficiently low temperatures. Once enriched, the gas will revert to its normal isomeric ratio over the course of hours or days, depending on the surface chemistry of the storage container. Although parahydrogen enjoys long lifetimes when stored in aluminum cylinders, the reconversion rate is significantly faster in glass containers due to the prevalence of paramagnetic impurities that are present within the glass. This accelerated reconversion is especially relevant for nuclear magnetic resonance (NMR) applications due to the use of glass sample tubes. The work presented here investigates how the parahydrogen reconversion rate is affected by surfactant coatings on the inside surface of valved borosilicate glass NMR sample tubes. Raman spectroscopy was used to monitor changes to the ratio of the (J: 0 → 2) vs. (J: 1 → 3) transitions that are indicative of the para and ortho spin isomers, respectively. Nine different silane and siloxane-based surfactants of varying size and branching structures were examined, and most increased the parahydrogen reconversion time by 1.5×-2× compared with equivalent sample tubes that were not treated with surfactant. This includes expanding the pH2 reconversion time from 280 min in a control sample to 625 min when the same tube is coated with (3-Glycidoxypropyl)trimethoxysilane.

A RARE CASE OF LITHIUM-INDUCED CARDIOTOXICITY IN THE SETTING OF ACUTE KIDNEY INJURY

Determination of degradation compounds of aged and deacidified papers requires an application of several analytical methods, including chromatographic and electrophoretic ones. Paper and paper extracts are very complex samples. Therefore, application of sample preparation methods is mostly involved in process of analysis. Sampling and sample preparation techniques provide transfer of analytes from a solid sample or from the gas phase (vapour) that exists above a solid sample into the extraction medium. Many extraction techniques were introduced, including conventional and advanced extractions utilizing water or organic extraction solvents, sampling tubes with adsorbents or fibre, often with the preconcentration of analytes. Passive sampling and solid-phase microextraction approaches were introduced as non-invasive techniques in the analysis of historical books and monitoring of indoor air in libraries and archives. This mini-review summarizes the sampling and sample preparation methods as well as new trends applicable in the analysis of degradation compounds of aged and deacidified papers.

Advanced sampling, sample preparation and combination of methods applicable in analysis of compounds in aged and deacidified papers. A minireview

Determination of degradation compounds of aged and deacidified papers requires an application of several analytical methods, including chromatographic and electrophoretic ones. Paper and paper extracts are very complex samples. Therefore, application of sample preparation methods is mostly involved in process of analysis. Sampling and sample preparation techniques provide transfer of analytes from a solid sample or from the gas phase (vapour) that exists above a solid sample into the extraction medium. Many extraction techniques were introduced, including conventional and advanced extractions utilizing water or organic extraction solvents, sampling tubes with adsorbents or fibre, often with the preconcentration of analytes. Passive sampling and solid-phase microextraction approaches were introduced as non-invasive techniques in the analysis of historical books and monitoring of indoor air in libraries and archives. This mini-review summarizes the sampling and sample preparation methods as well as new trends applicable in the analysis of degradation compounds of aged and deacidified papers.

Implementation of BRCA mutations testing in formalin-fixed paraffin-embedded (FFPE) samples of different cancer types.

BRCA1 and BRCA2 are onco-suppressor genes involved in the DNA repair mechanism. The presence of BRCA1/2 mutations confers a higher risk of developing several cancer types. To date, the FDA approved various PARP inhibitors to treat selected BRCA1/2 mutated oncologic patients. At first, PARP inhibitors were approved for patients with ovarian and breast cancers, and subsequently for metastatic pancreatic adenocarcinoma and metastatic castration-resistant prostate cancer after the treatment with chemotherapy. The current guidelines for BRCA testing are very heterogeneous between the different types of tumors regarding the diagnostic algorithm and the type of sample to analyze, such as the blood for the germline mutations and the tumoral tissue for the somatic mutations. Few data have currently been described regarding the detection of BRCA1/2 somatic mutations in formalin-fixed paraffin-embedded (FFPE) samples. In this review, we propose an overview of the BRCA mutations in FFPE samples of several cancers, including breast, ovarian, fallopian tube, primary peritoneal, prostate, and pancreatic cancer. We summarize the types and the frequency of BRCA mutations, the guidelines approved for the test, the molecular assays used for the detection and the PARP inhibitors approved for each tumor type.

Fast In Situ Inactivation of Pathogens in Tubes by Plasma

During the COVID-19 pandemic, the prevailing method for inactivating samples used in nucleic acid detection is a time-consuming process that involves heating the samples in a thermostatic water bath at 56 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> C for a duration of 30 min. In this study, a fast in situ inactivation method for pathogen samples in test tubes was proposed, which can markedly reduce the treatment time of pathogens to 2 min without affecting subsequent detection. By attaching a designed needle-electrode structure to the samples, an inactivation device of corona discharge was implemented. Using the device, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Escherichia coli</i> could be inactivated by more than 3 Log in 1 min and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Mouse Hepatitis Virus</i> (MHV) within 2 min. In addition, the ribonucleic acid (RNA) damage of MHV, obviously ahead of its inactivation, is suggested not to be the main reason that causes its inactivation. So locating an appropriate treatment duration can preserve the RNA of samples for nucleic acid detection. In the future study, proposing a new discharge structure with electrodes outside the sealed test tube will be our focus.

A miniaturised fetch rover concept for Mars sample return

In the context of the NASA/ESA Mars Sample Return (MSR) Campaign a Sample Fetch Rover (SFR) has been studied to acquire sample tubes cached on the surface by NASA's Perseverance rover and return them to the Sample Retrieval Lander (SRL) for launch into Mars orbit. The current SFR design, similar in size to ESA's ExoMars Rover, faced significant challenges in terms of accommodation on the lander. An alternative mini Sample Fetch Rover (mSFR) concept is explored in response to these challenges, aiming at a mass target around 20 kg. The miniaturised rover is assessed against some reduced mission requirements to evaluate its usefulness for MSR. The main areas of the mSFR design are discussed herein, with particular attention to traverse and tube fetching strategy. The study suggests that the concept is feasible and could be accommodated on SRL with minimum impact to the lander's design. Furthermore, preliminary analysis shows how the small vehicle could perform a useful role in MSR, making it particularly attractive as a simple backup to other tube delivery methods. Lastly, future investigations and areas of improvement are suggested.

Using fecal immmunochemical cartridges for gut microbiome analysis within a colorectal cancer screening program

ABSTRACT The colorectal cancer (CRC) screening program B-PREDICT is an invited two-stage screening project using a fecal immunochemical test (FIT) for initial screening followed by a colonoscopy for those with a positive FIT. Since the gut microbiome likely plays a role in the etiology of CRC, microbiome-based biomarkers in combination with FIT could be a promising tool for optimizing CRC screening. Therefore, we evaluated the usability of FIT cartridges for microbiome analysis and compared it to Stool Collection and Preservation Tubes. Corresponding FIT cartridges as well as Stool Collection and Preservation Tubes were collected from participants of the B-PREDICT screening program to perform 16S rRNA gene sequencing. We calculated intraclass correlation coefficients (ICCs) based on center log ratio transformed abundances and used ALDEx2 to test for significantly differential abundant taxa between the two sample types. Additionally, FIT and Stool Collection and Preservation Tube triplicate samples were obtained from volunteers to estimate variance components of microbial abundances. FIT and Preservation Tube samples produce highly similar microbiome profiles which cluster according to subject. Significant differences between the two sample types can be found for abundances of some bacterial taxa (e.g. 33 genera) but are minor compared to the differences between the subjects. Analysis of triplicate samples revealed slightly worse repeatability of results for FIT than for Preservation Tube samples. Our findings indicate that FIT cartridges are appropriate for gut microbiome analysis nested within CRC screening programs.

Stable dispersions of double-walled carbon nanotubes for carbon nanotube/copper co-deposition

This work explores a novel approach to disperse purified double-walled carbon nanotubes in high ionic strength aqueous media, i.e. a copper ion solution to further prepare double-walled carbon nanotubes/Cu composites by co-electrodeposition. Firstly, the metal catalyst impurities in the tube samples are selectively removed by a one-pot gas-phase purification treatment. Two non-ionic (Triton X-100 and Pluronic-P123) and one anionic (sodium dodecyl sulfate) surfactant were used to disperse the purified samples by varying the carbon nanotubes/surfactant ratio and the surfactant content. Triton X-100 is a poly(ethylene glycol) in which one of the terminal hydroxy groups has been converted into the corresponding p-(2,4,4-trimethylpentan-3-yl)phenyl ether. Pluronic-P123 is a triblock copolymer comprising poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) leading to PEO-PPO-PEO. Sodium dodecyl sulfate of chemical formula C12H25OSO2ONa possesses a sulfate head and a hydrocarbon tail. The capability of each surfactant to disperse the double-walled carbon nanotubes in the copper ion solution is analyzed and later discussed based on the nature of the inter-tube forces. Among the employed surfactants, Pluronic-P123 exhibits the best dispersive level since stable and homogenous suspensions of double-walled carbon nanotubes are obtained. The dispersion mechanism proposes that the hydrophobic nature of Pluronic-P123 promotes efficient steric repulsions allowing the stable dispersion in the copper electrolyte. The samples dispersed by this way are successfully co-deposited and they form well-distributed double-walled carbon nanotubes within the copper matrix. The obtained results are an important step on the way to achieving an efficient double-walled carbon nanotubes/Cu composite synthesized by electrodeposition means.

Water Wall Tubes’ High Temperature Corrosion Root Cause Investigation: A 300 MW Level Boiler Case

High temperature corrosion poses a great threat to boiler water wall safe operation. To investigate the corrosion root cause, a 300 MW level boiler water wall high temperature H2S corrosion case was reported. The typical hydrogen sulfide H2S corrosion feature was large amounts of sulfur which could be found in the cut down sample tube corrosion layer, with a thickness of 482 μm. In addition, huge amounts of lead (Pb) could be found in the corrosion layer, which resulted from the lead sulfide (PbS) deposition when the high temperature flue gas condensed at the water wall tubes. Meanwhile, the sulfur in the corrosion layer was closely related to the H2S concentration in the water wall ambience. The related ambience test showed that the H2S could achieve up to 1000 ppm when the boiler was in operation, far larger than the suggested reference value of 100 ppm. Hence, the overlarge H2S concentration was a vital factor for the tube corrosion. To further investigate the reason why the H2S was kept in such high concentration in the boiler long term operation, and the reasons for the over-high sulfur content in the coal and the over-large diameter of the imaginary circle of primary air (DICPA), two factors were obtained. The peak sulfur content reached 2.5% and the suggested sulfur content was below 1%. The DICPA was so large (1580 mm) that the pulverized coal easily scoured the water wall tubes, which would boost the thinning process of the tubes. To relieve the high temperature corrosion, improve the coal qualities, decrease the DICPA, adjust the operation diameter and adopt a coating technology four measures were suggested.

Effects of Oxide Fragments on Microstructure and Mechanical Properties of AA6061 Aluminum Alloy Tube Fabricated by Thermomechanical Consolidation of Machining Chips

An AA6061 aluminum alloy tube was fabricated by compacting machining chips via thermomechanical consolidation, including hot pressing and hot extrusion. The microstructure evolution and formation of oxide particles were investigated in correlation to tensile mechanical properties. It was found that fine Al/Mg oxide particles were formed due to the fracture of oxide layers on the chips and the reaction between Mg and Al2O3 during hot extrusion. The oxide particles inhibited the growth of recrystallized α-Al grains, leading to the formation of a microstructure consisting of coarse elongated grains with sizes of 420 μm and fine equiaxed grains with sizes of 10 μm. After T6 heat treatment, a microstructure with finer grains (grain sizes: 34 μm) formed due to further recrystallization induced by residual strain. The tensile mechanical properties testing results indicated that a good combination of strength (296 MPa) and ductility (7.6%) was achieved in the T6 heat treated samples, which were likely attributed to the high-quality inter-chip bonding, as well as the fine oxide particles which were small enough that further crack nucleation and growth around them were inhibited during tensile deformation. For the purpose of comparison, the microstructure and mechanical properties of the as-extruded and T6 heat treated samples produced by hot extrusion of the cast ingot of AA6061 aluminum alloy were also investigated. The lower tensile strength of solid-state recycled tube sample might be associated with the consumption of Mg atoms by the oxidation reaction, leading to the lower density of β″ precipitates in precipitation strengthening.