Vacuum Treatment Research Articles

Production of improved quality steel in highscale basic oxygen furnaces using vacuum treatment

The article presents the results of the converter steel technology development using ladle treatment including portion vacuum degassing at vessel UPVS-350 and pouring at continuous casting machine. In order to improve the quality of metal products, steels of grades 3sp, 08sp, 20k, 20sp, 09G2S, 10G2S1D, 09G2S, 08GT, 17G1SU, 17G1S, 17GS, 10HSND, 15HSND, E36, pipe steels of type 09G2FB were treated by vacuum. Steel was smelted in basic oxygen furnaces with a capacity of 350 ton using technical pure oxygen (99,2–99,5% О2). The article shows that with a UPVS-350 vacuum chamber dilution to133 Pa (1 mm Hg), a metal portion weight of 20–40 tons, the number of vacuum ing cycles less than 25 and a circulation coefficient from 2 to 5, a degree of oxygen removal of up to 40%and hydrogen up to 50% can be achieved. There is an improvement in the pouring ability of vacuum treated steel, a decrease in the axial discontinuity (stratification)at the central part of the slabs from 3 to 2–2.5 grades, decrease of the nonmetallic inclusions content in the billets by 0,2–2,3 grade and their distribution in the volume of metal is more uniform. When exhaustion in a vacuum chamber reach of 1–2 mm Hg level, the impact toughness and elongation of steel in crease. For carbon steel, the production of inappropriate quality metal according to the ultrasonic control decreased by about 3 times (from 0,39 to 0,12%), and the total degree of the rejected metal decreased from 1,06 to 0,65%. During vacuuming of 08GT steel using for chemical reactors, there is a more compact and greater uniformity of the ferrite-perlite structure with the value of the actual grain no. 7–9. The internal structure at the liquation central zone of the sheets produced of this steel is also improved

Mass transfer kinetics of ultrasonic- and vacuum-ultrasonic-assisted static brine of chicken breast (Pectoralis major).

The aim of this study was to investigate the effect of different ultrasound treatment (UT) conditions (Control, UT-150, UT-300, UT-450, Vacuum-UT-150, Vacuum-UT-300, Vacuum-UT-450) on the brining kinetics and meat quality of chicken breast. The results showed that vacuum-ultrasonic-assisted treatment greatly accelerated the transfer of moisture and NaCl, and the highest yield was obtained by ultrasonic power of 450W. The mass transfer kinetics (k1 and k2) were significantly related to vacuum pretreatment and ultrasonic power. The values of k1 for total and moisture weight changes decreased with the increase of ultrasonic power, whereas the values of k2 increased with vacuum pretreatment. The application of ultrasound treatment with vacuum improved the NaCl effective diffusion coefficients (De) from 1.189×10-9 to 1.308-1.449×10-9 m2/s, and the highest De was found with Vacuum-UT-450. The treatment of ultrasound and vacuum can reduce shear force and enhance the water-holding capacity (WHC). According to the analysis of water distribution, vacuum and ultrasound could decrease the T23 values, indicating that the mobility of water decreased. The result of microscopic observation further supported that the disruption of myofibrils was related to the tenderness and WHC changes, which was caused by vacuum and ultrasound treatment. Thus, Vacuum-UT brining could be employed as an emerging technology for improving the efficiency of brining and meat quality of other meat. PRACTICAL APPLICATION: Vacuum-ultrasonic-assisted static brine is an effective and feasible treatment to replace tumbling treatment for maintaining the integrity of the muscle bundles and accelerating the brining rate.

Anastomotic leakage following surgical resection in the upper gastrointestinal tract

Surgical resection is the consistent component of curative treatment strategies for primary malignant diseases of the stomach and the esophagus. The placement of anastomoses for the necessary reconstruction still accounts for substantial morbidity and in the case of afailure to rescue also for mortality, especially for esophagojejunostomy and esophagogastrostomy. The diagnostics of anastomotic leakage routinely involve computed tomography and endoscopy and timely performance appears to be essential. Endoscopy can simultaneously initiate the essential treatment step. Amajor reason for the improvement of postoperative outcomes after resection in the upper gastrointestinal tract in the last decades is the successful and mostly endoscopically performed management of anastomotic leakage, whereby different endoscopic treatment options are now available. Endoscopic vacuum therapy has become established as the standard, normally with an endoscopic vacuum sponge technique but is also now supplemented by acombination system of vacuum sponge and stent. Furthermore, afoil-coated multiple lumen nasogastric tube represents another available option, which can possibly especially be used as aprophylactic measure. The longest established endoscopic therapy option for anastomotic leaks, the endoluminal metal stent, has been replaced as the standard by the vacuum treatment but is still used in suitable situations. Additionally, there are endoscopic suture devices that are currently only used very occasionally. Surgical revision is always available as treatment escalation but is only recommended for very early occurrences and possibly technically related anastomotic leakage and in the case of failure of endoscopic treatment. This article describes and summarizes the diagnostics and treatment of anastomotic leakages after surgical procedures of the upper gastrointestinal tract.

Cu Evaporation from Liquid Iron Alloy in Stream

The accumulation of copper in steel scrap is becoming an increasingly problematic issue in the steelmaking industry. Accordingly, the present study was undertaken to investigate the removal of copper from a liquid Fe–Cu alloy via tapping under vacuum. Furthermore, the impact of surface-active components sulfur and oxygen was examined. For this purpose, four Fe–0.5 wt% Cu alloys with varying oxygen and sulfur contents were melted and subsequently poured at a pressure of 100 Pa. The findings indicate that alloys with low oxygen and sulfur content exhibited enhanced copper evaporation. Additionally, the evaporation of other tramp metals, including manganese, phosphorus, and tin, was observed, and the influence of sulfur and oxygen on this process was discussed. Furthermore, the vacuum treatment conditions for copper evaporation in industrial settings were explored.

Inclusion Transfer Phenomenon under Unsteady Multiphase Flow during Rheinstahl–Heraeus Vacuum Treatment Process

Inclusion particles are extremely harmful to the quality of steel products, and Rheinstahl–Heraeus (RH) vacuum treatment is the key process to remove the inclusions from molten steel. By coupling analyzing the unsteady gas–liquid flow and decarbonization reaction, the inclusion mass/population conservation model is developed to explore the inclusion particles transfer phenomenon during RH vacuum treatment process. The coupling mathematical models are validated by the metallurgical experimental data. The results show that the predicted inclusion mass concentration in unsteady CO–Ar–molten steel multiphase system has significantly smaller relative error than that in steady Ar–molten steel flow. CO bubble plays a key role in the inclusion transfer phenomenon, which prompts the inclusion transport, the collision‐aggregation, and the removal process. At the 4th minute of vacuum treatment, the average inclusion volume concentration and the average inclusion number density in CO–Ar–molten steel are 72.75% and 64.62% of those in Ar–molten steel, respectively. The average inclusion characteristic radius in CO–Ar–molten steel is 7.33% larger than that in Ar–molten steel.

The effect of complex extra-furnace treatment of metal melts on the formation of non-metallic inclusions in large-sized ingots

Abstract The article presents the results of studying non-metallic inclusions (NI) after extra-furnace treatment of the 13Cr9Mo2Co1NiVNbNB steel melt to produce large-sized ingots. The objects of the study were laboratory samples melted in a semi-industrial induction furnace with the capacity of 20 tons (the first batch), and samples obtained after melting in an electric arc furnace with the capacity of 120 tons, followed by modification and double vacuuming (the second batch).
Previously, using the Fact Sage software, modeling of the NI formation processes was carried out. The data were obtained on the possible NI composition and amount in this steel.
Studying NIs (the composition, the contamination index, inclusion parameters) was carried out on an ASPEX Explorer electron microscope using the method of automatic X-ray spectral analysis of particles (Automatic Features Analysis, AFA). It was established that in the samples of the first batch, the main part of the NIs consisted of chromium- and manganese-containing oxides: chromium-manganese spinels (Cr-Mn-O and Mn-Cr-Si-O groups), which occupy more than 94% of the total area of the NIs. In the samples of the second batch, the main part of the Nis was represented by Cr-Mn-O; Al-Cr-O; Cr-Al-Mn-O systems.
It was shown that the average size of non-ferrous substances in the samples of the laboratory batch and in industrial samples after extra-furnace treatment differs slightly (5-12%), however, the contamination index in industrial samples after vacuum treatment and especially after modification and repeated vacuum treatment was reduced by more than 10 times. The results obtained allow recommending vacuum treatment and complex modification with calcium and boron as measures to prevent the formation of non-ferrous metals and to improve metallurgical quality when smelting large ingots using complex alloy steels.

Factors Affecting the Adhesion of Flour Particles to Stainless-steel Surfaces and Vacuum Dry-cleaning

Recent outbreaks and recalls linked to flour-based products have highlighted the need for improved cleaning methods in low-moisture environments. The factors affecting adhesion forces of flour particles, and the vacuum cleaning methodologies to overcome these forces, need to be better understood. The objectives of this study were to: (1) Measure electrostatic charge build-up in flour under different environmental conditions (20, 40, 60% relative humidity at room temperature), (2) quantify how powder size (US standard No. 60–80 or 80–100 mesh), electrostatic charge (charged and uncharged), and relative humidity impact the force required to remove the powder from an electropolished 304 stainless steel coupon (8 × 8 × 0.2 cm), and (3) determine the most effective vacuum nozzle angle (0, 45, 90° relative to the surface) for cleaning. Chargeability (nC) of flour samples was assessed using Faraday cup electrometry, while the surface adhesion force of the flour particles was measured using a custom-built impact tester. The surface cleanliness after vacuum treatments was assessed using ATP (adenosine triphosphate) swabs and a luminometer. Charged flour samples at 20% relative humidity (RH) exhibited a significantly higher charge compared to those at 40 and 60% RH. Within the 60–80 mesh range, charged flour showed higher adhesion rates than uncharged samples at both 20 and 40% RH. However, in the 80–100 mesh range, charged flour did not show a significant difference in adhesion when compared to uncharged samples at any RH level. Additionally, at 60% RH, surface residues measured by ATP were significantly lower for a vacuum angle of 90° than for 0° across both 60–80 mesh and 80–100 mesh size ranges of wheat flour. The vacuum cleaning treatment proved capable of overcoming the increase in adhesion from triboelectric forces; however, trace flour residues were still detected on stainless steel surfaces postvacuuming, indicating that vacuuming alone may be insufficient.

Effects of aggregates and fibers on the strength and permeability of concrete exposed to low vacuum environment

The performance and regulation of concrete in low vacuum environments are receiving increasing attention. This study investigates the effects of aggregates and fibers on the strength and permeability of concrete in a low vacuum environment, using varying gradients of sand ratios (37.5 %, 40 %, and 42 %) and aggregate-to-binder ratios (3.27, 3.92, and 4.14). Three types of non-metallic fibers are utilized: polyethylene (PE), polyvinyl alcohol (PVA), and glass fibers. Evaluations focus on concrete strength, mass loss, gas permeability, capillary water absorption, and porosity. Results indicate that higher sand and aggregate-to-binder ratios enhance both flexural and compressive strength. Fiber incorporation improves flexural and compressive toughness, with PE fibers showing the most significant toughening effect. The low vacuum environment increases the strength of the concrete but reduces its axial compression toughness ratio and increases brittleness, while fiber incorporation helps improve the compression toughness of the concrete. Higher sand and aggregate-to-binder ratios reduce mass loss and accelerate drying equilibrium, while fibers increase mass loss and prolong drying equilibrium, with PVA fibers causing greater mass loss. The pattern of concrete mass loss can be explained by the tortuosity of the moisture diffusion path. Additionally, low vacuum significantly increases the gas permeability of concrete. Enhancing the sand and aggregate-to-binder ratios reduces permeability both before and after low vacuum treatment. Although fibers increase the gas permeability, they help mitigate this increase under low vacuum condition. Capillary water absorption tests reveal that concrete under low vacuum condition has a significantly higher water absorption rate compared to air-drying condition. Increasing sand and aggregate-to-binder ratios reduces water absorption and capillary water content, whereas fibers have the opposite effect. Porosity tests show that moisture migration in a low vacuum environment is mainly related to permeable porosity, while total porosity is more closely related to compressive strength.

Effects of Corm Treatment with Cold Plasma and Electromagnetic Field on Growth and Production of Saffron Metabolites in Crocus sativus.

Crocus sativus L. is a widely cultivated traditional plant for obtaining dried red stigmas known as "saffron," the most expensive spice in the world. The response of C. sativus to pre-sowing processing of corms with cold plasma (CP, 3 and 5 min), vacuum (3 min), and electromagnetic field (EMF, 5 min) was assessed to verify how such treatments affect plant performance and the quality and yield of herbal raw materials. The results show that applied physical stressors did not affect the viability of corms but caused stressor-dependent changes in the kinetics of sprouting, growth parameters, leaf trichome density, and secondary metabolite content in stigmas. The effect of CP treatment on plant growth and metabolite content was negative, but all stressors significantly (by 42-74%) increased the number of leaf trichomes. CP3 treatment significantly decreased the length and dry weight of flowers by 43% and 60%, respectively, while EMF treatment increased the length of flowers by 27%. However, longer CP treatment (5 min) delayed germination. Vacuum treatment improved the uniformity of germination by 28% but caused smaller changes in the content of stigma compounds compared with CP and EMF. Twenty-six compounds were identified in total in Crocus stigma samples by the HPLC-DAD method, including 23 crocins, rutin, picrocrocin, and safranal. Processing of Crocus corms with EMF showed the greatest efficiency in increasing the production of secondary metabolites in saffron. EMF increased the content of marker compounds in stigmas (crocin 4: from 8.95 to 431.17 mg/g; crocin 3: from 6.27 to 164.86 mg/g; picrocrocin: from 0.4 to 1.0 mg/g), although the observed effects on growth were neutral or slightly positive. The obtained findings indicate that treatment of C. sativus corms with EMF has the potential application for increasing the quality of saffron by enhancing the amounts of biologically active compounds.

15 Years of Vacuum Bell Therapy for Pectus Excavatum: Long-term Outcomes and Influencing Factors

BackgroundLong-term results and factors affecting outcomes of vacuum bell therapy for pectus excavatum are relatively unknown. MethodsWe conducted a retrospective study on patients (<18y) treated with vacuum bell therapy between May 2008 and October 2021. Primary outcome was treatment success; secondary outcomes were analysis of daily time spent on treatment, treatment duration, complications, long-term follow-up, treatment for patients awaiting a Nuss procedure, treatment for female patients, and factors affecting outcomes. ResultsOf 259 patients treated with vacuum bell therapy, 18.9% (n = 49/259) were still being treated, 17.4% (n = 45/259) were lost to follow-up and 63.7% (n = 165/259) completed treatment, with a 52.1% (n = 86/165) success rate. Median follow-up was 64.0 months (interquartile range 48.0–87.0). More time spent daily on vacuum bell therapy, total treatment duration, and overnight use led to a higher success rate (P = 0.002, P < 0.001, P < 0.001 resp.). Complications (22.8%, n = 59/259) were minor, recurrence occurred in 2.3% (n = 2/86) of patients. Of the patients treated while awaiting a Nuss procedure, 26.7% (n = 4/15) no longer required the Nuss procedure. Breast growth made 39.3% (n = 11/28) of female patients quit treatment. Deeper deformities (P = 0.02, P = 0.009), flexible chest wall (P = 0.007) and symptomatic pectus excavatum (P = 0.02) resulted in lower success rates. ConclusionsVacuum bell therapy is successful in up to 52.1% of patients. Overnight vacuum bell use and treatment while awaiting a Nuss procedure should be encouraged. Older patients with a stiff chest wall can be successfully treated with prolonged treatment. For female patients watchful waiting or early treatment, to prevent challenges during breast growth, is preferred. Level of evidenceLevel II.

Effect of vacuum combined with ultrasound on color protection of pomegranate juice

AbstractPomegranate juice is prone to color fission during processing and storage due to the instability of anthocyanins, resulting in significant economic losses. This study aims to inhibit the browning of pomegranate juice during processing using the combined technology of vacuum and ultrasound for maintaining its color as much as possible. Pomegranate juice was treated with vacuum (0.5 MPa) and ultrasound (300, 600, 900, 1200, and 1500 W; 15, 20, 25, 30, and 35 min), respectively, to investigate the effects on the color, antioxidant capacity, anthocyanin/polyphenol content, and polyphenol oxidase activity of pomegranate juice. The results showed that the combined treatment of vacuum and ultrasound had a better effect on improving the total anthocyanin content of pomegranate juice than vacuum or ultrasound treatment alone. Vacuum combined with ultrasound can reduce the browning during pomegranate juice processing, increasing browning inhibition rates by 46.01% and 46.19%; reduce the activity of PPO enzyme and increase the inhibition rate of PPO enzyme activity by 35.58%; maintain a high total phenolic content, increasing the total phenolic content of pomegranate juice by 29.27% and 33.79%, respectively; and improve the ABTS scavenging rates by 2.89% and 1.92%, and increase DPPH scavenging rates by 1.35% and 3.01%. Moreover, vacuum ultrasound treatment had no significant effect on the odor of pomegranate juice. Vacuum combined with ultrasonic treatment is beneficial for protecting the color of pomegranate juice and improving its antioxidant performance during the processing. Therefore, combined technology of vacuum and ultrasound would be a promising method for future food processing.Practical applicationsThis study provides a simple and novel method for protecting the color of pomegranate juice during processing. The combination of vacuum and ultrasound has a certain protective effect on the color of pomegranate juice during processing, and also provides new ideas for color protection research.

Enhancing virus-induced gene silencing efficiency in tea plants (Camellia sinensis L.) and the functional analysis of CsPDS

Virus-induced gene silencing (VIGS) is an effective technology for gene functional analysis in tea plants, yet its efficiency needs enhancement, particularly in the Qiancha 1 (QC1) cultivar of Camellia sinensis. Employing pTRV1/pTRV2-CsPDS as a vector and leaf albinism rate as a silencing index, this study optimized the VIGS system by examining the effects of vacuum treatment duration, pressure, injection method, and cutting size on silencing efficiency. The results indicate that both injection and vacuum infiltration methods are viable in QC1, with the vacuum method exhibiting superior efficiency. The optimal vacuum infiltration conditions were determined to be 0.8 kPa for approximately 5 min. Phenotypic analysis showed that silencing the CsPDS gene resulted in leaves yellowing to varying degrees. Transcriptome analysis revealed disruptions in various pathways in these tea cuttings with differing levels of coloration, particularly in photosynthetic pigment biosynthesis and nitrogen metabolism. Interestingly, the content of theanine was higher in the cuttings with lower chlorophyll content. Analysis of differential gene expression profile and quantitative real-time PCR confirms that theanine accumulation is primarily due to increased synthesis and reduced degradation. These findings deepen our understanding of the metabolic and molecular mechanisms behind leaf coloration in tea plants.

Thermoforming Vacuum Packaging Influences Fresh Pork Loin Chop Characteristics.

The storage duration of fresh meat products is a contributing factor leading to increased waste and loss at the retail counter. Losses of fresh pork can be linked to packaging methods that do not protect the attributes of color, taste, and odors consumers use in determining wholesome meat. Boneless pork loins (N = 63) were fabricated into 2.54-cm-thick chops and assigned to one of three vacuum treatments (VacA, VacB, VacC) or a fourth polyvinyl chloride overwrap (PVC) treatment to assess objective fresh color, cook loss, Warner-Bratzler shear force (WBSF), and lipid oxidation. Pork chops (n = 882) were evaluated at 5-day intervals (D 0, 5, 10, 15) in a randomized complete block design. Pork chop surface color was lighter (L*; p < 0.0001) when stored in a vacuum compared to PVC-packaged loin chops, regardless of storage duration. Redness (a*) values were greater (p < 0.0001) for loin chops stored in PVC than all other vacuum packaging treatments throughout the entire 15-day display period. Relative values for chroma on PVC-packaged loin chops were greater (p < 0.0001) throughout the simulated retail display period. An interaction of day and packaging treatment (p < 0.0343) occurred for WBSF. Lipid oxidation for pork chops packaged using PVC was significantly greater (p < 0.0001) from Day 10 through the completion of the storage period. Results indicate that vacuum packaging limits the deterioration of fresh pork loin chops, whereas traditional overwrapping expedites the color and lipid oxidation during refrigerated storage.

Chemical and UV Durability of Hydrophobic and Icephobic Surface Layers on Femtosecond Laser Structured Stainless Steel

Femtosecond laser processing significantly alters the surface structure and chemical composition, impacting its wetting properties. Post-treatments such as immersion in a hydrocarbon liquid (petrol) or storage in a vacuum can significantly reduce ice adhesion, making the surfaces interesting for anti-ice applications. This study investigates their durability against acetone, ethylene glycol, and UV radiation. The laser-structured surfaces were immersed in the respective liquids for up to 48 h. The results indicate limited durability of the superhydrophobic and icephobic layers when submerged in acetone and ethylene glycol, with more favorable results for petrol treatment than vacuum treatment. Similar results were obtained after 100 h of UV exposure, showing a decrease in superhydrophobic properties and an increase in ice adhesion. However, repeated vacuum treatments conducted after the chemical durability tests revealed the potential for partial recovery of the hydrophobic and icephobic properties. XPS analysis was performed throughout the experiments to evaluate changes in surface chemistry resulting from the post-laser treatments and the durability tests.

Process Optimization and Quality Components Analysis of γ-Aminobutyric Acid Pickled Tea.

Pickled tea is an anaerobically fermented tea common in Thailand, Myanmar and Yunnan minority areas. γ-aminobutyric acid (GABA) is non-protein amino acid with multiple bioactives, which can be easily produced under anaerobic conditions. During the processing of pickled tea, controlling the process parameters is effective for the production of GABA-rich products; however, the precise parameters remain to be clarified. In the present study, the fresh leaves of Camellia sinensis (L.) Kuntze (C. sinensis) 'FudingDabai', C. sinensis 'MabianLv No. 1', C. sinensis 'Wuniuzao' and C. sinensis 'Fuxuan No. 9' were used as raw materials to process GABA-rich pickled tea. Single-factor and orthogonal experiments were conducted to determine the best tea cultivars and optimize the best processing parameters via comparing the content of GABA, tea polyphenols (TPs) and other biochemical components of GABA-rich pickled tea. The results of the signal-factor experiment showed that the fresh leaves of C. sinensis 'MabianLv No. 1' had the highest GABA content of 2.61 mg·g-1 after treatment with vacuum for 6 h; therefore, C. sinensis 'MabianLv No. 1' was selected as the raw material for the subsequent experiments. Orthogonal experiments showed that the highest GABA content of 2.53 mg·g-1 was found in the pickled tea with 8 h of vacuum treatment, 20 min of rolling after microwave fixing, 20 min of spreading and 20 d of anaerobic fermentation at room temperature. Further, the sensory evaluation showed that it possesses a strong sour taste with a slight sweetness and a light yellow color and better comprehensive quality. This indicates that these parameters are optimal for the processing of GABA-rich pickled tea. This study will provide scientific basis for the subsequent production of high GABA tea.

Predicting the Liquid Steel End-Point Temperature during the Vacuum Tank Degassing Process Using Machine Learning Modeling

The present work focuses on predicting the steel melt temperature following the vacuum treatment step in a vacuum tank degasser (VTD). The primary objective is to establish a comprehensive methodology for developing and validating machine learning (ML) models within this context. Another objective is to evaluate the model by analyzing the alignment of the SHAP values with metallurgical domain expectations, thereby validating the model’s predictions from a metallurgical perspective. The proposed methodology employs a Random Forest model, incorporating a grid search with domain-informed variables grouped into batches, and a robust model-selection criterion that ensures optimal predictive performance, while keeping the model as simple and stable as possible. Furthermore, the Shapley Additive Explanations (SHAP) algorithm is employed to interpret the model’s predictions. The selected model achieved a mean adjusted R2 of 0.631 and a hit ratio of 75.3% for a prediction error within ±5 °C. Despite the moderate predictive performance, SHAP highlighted several aspects consistent with metallurgical domain expertise, emphasizing the importance of domain knowledge in interpreting ML models. Improving data quality and refining the model framework could enhance predictive performance.

Hydration and microstructure evolution of cement paste in low vacuum environments

Low vacuum is one of the most challenging service environments for cementitious materials, which would affect their hydration and microstructure, and thereby impair strength and durability. In this study, the hydration phases and microstructural evolution of pastes based on Portland cement (PC), sulphoaluminate cement (SAC), and tricalcium silicate (C3S, the clinker of PC) were investigated under low vacuum conditions. The results show that rapid mass loss could be observed at the initial stage of low vacuum treatment, which was mainly attributed to the dissipation of free water. After that, the mass loss rate was greatly slowed down and maintained at a relatively low level, which was primarily due to the loss of chemical bound water in hydration products. As a result, C3S samples, with the slowest early hydration procedure, exhibited the highest mass loss, which was followed by PC and SAC samples. The dissipation effect by low vacuum treatment resulted in the inhabitation of cement hydration, and correspondingly the contents of hydration products remained almost constant, or even decreased especially for ettringite (AFt). Moreover, the examination of the hydration product morphology demonstrates that under low vacuum conditions, the needle-like morphology of the hydration product C-S-H transferred gradually from divergence to convergence or underwent collapse, while the AFt crystals experienced degradation and then transformed into an amorphous state. This consequently led to the sample after low vacuum treatment exhibiting increased total volume of pores less than 100 nm and elevated percentage of pores with sizes from 50 nm to 100 nm. Overall, this research holds great scientific significance in guiding the engineering application of concrete in low vacuum environments.

Low-oxygen silicon preparation using vacuum treatment by oxidation control and moisture removal kinetics investigation

Diamond wire saw silicon powder (DWSSP) is a waste produced during silicon wafer processing for photovoltaic (PV) modules, and it shows significant reutilization potential. However, the presence of moisture leads to silicon oxidation and the formation of a surface SiO2 layer that hinders the recovery of high-purity silicon. In this study, vacuum treatment (VT) was used to prepare low-oxygen silicon by controlling the oxidation and removing moisture from DWSSP waste, thus preventing SiO2 layer formation. The oxygen content in DWSSP decreased by 15.01 %, from 7.26 % to 6.17 %, and the SiO2 layer thickness also decreased by 10.29 %, from 2.04 nm to 1.83 nm after the VT process. Additionally, the VT process lowered the moisture boiling point, facilitating surface evaporation and internal diffusion of moisture. This increased the moisture effective diffusion coefficient from 5.16 × 10−10–6.16 × 10−9 m2 s−1 to 1.21 × 10−9–6.88 × 10−9 m2 s−1 and reduced the apparent activation energy from 32.17 kJ mol−1 to 16.05 kJ mol−1. The efficient moisture removal of VT inhibited the growth of the SiO2 layer to enable the preparation of low-oxygen silicon during silicon recovery.

Selective CO2 adsorption over a Zr-based metal–organic framework functionalized with tris(2-aminoethyl)amine

Selective capture of CO2 from off-gas or even the atmosphere is very important against global warming. In this work, a stable Zr-based MOF (MOF-808) was loaded with –COOH group and was further functionalized with tris(2-aminoethyl)amine (TREN), via a reaction between –NH2 of TREN and –COOH sites. The derived materials were analyzed with X-ray diffraction, scanning electron microscopy, FTIR, X-ray photoelectron spectroscopy, thermogravimetry analysis, elemental analysis, and nitrogen adsorption at 77 K; utilized in the adsorption of CO2 and N2 at relatively low pressure up to 100 kPa. One functionalized MOF-808 prepared in this work (named MOF808-EDTA-TREN(0.3)) showed remarkable performances in the selective capture of CO2 under low pressure. For example, the invented MOF exhibited the highest selectivity (based on ideal adsorbed solution theory) in CO2 capture from N2 and CO2 (SCO2/N2: 519 at 100 kPa) compared with any reported results, thus far, using MOF-808-based materials. Moreover, MOF808-EDTA-TREN(0.3) was recyclable up to the fifth run upon vacuum treatment. The noticeable performances of MOF808-EDTA-TREN(0.3) in CO2 adsorption could be explained by the loaded –NH2 sites of TREN (that are effective in carbamates formation) and bulky TREN that decreases the nitrogen adsorption because of the reduced porosity of the MOF. In brief, loading bulky amines with ample amino groups like TREN can be suggested as an attractive way to modify a MOF for selective CO2 capture from off-gas of various industries.

Preparation and drying characteristics of poplar wood modified by hexacyclite

In recent decades, wood drying has emerged as an important method to ensure wood quality and improve wood utilization. However, the addition of modifiers to wood can hinder the transfer of moisture, making the drying process difficult. Therefore, the drying of modified wood is challenging. This study focuses on poplar wood and reports the preparation of modified wood capable of releasing health-beneficial negative oxygen ions. In particular, this study examined the effect of hexacyclite on the transfer of internal moisture and heat in wood. Hexacyclite was dispersed using sodium hexametaphosphate as a dispersing agent, and the modified poplar wood was prepared via vacuum pressure impregnation. The process involved six cycles of the following treatments: a vacuum treatment (−0.08 MPa, 20 min), followed by a pressure treatment (1 MPa, 120 min), and a final atmospheric treatment (5 min). The modified wood was dried via kiln drying, during which the overall wood temperature rapidly increased, with the total drying rate also increasing by 1.05%/h. The introduction of hexacyclite potentially altered the way modified wood bound with moisture, leading to permanent changes in the porosity of cell walls and the structure of polymers and thus altering the movement of water molecules. The modified wood continuously emitted far-infrared rays with a wavelength of 8–15 μm. In some large water clusters, after the far-infrared energy was absorbed, the movement of water molecules accelerated, thereby increasing the drying rate in the wood below the fiber saturation point. Ultimately, this resulted in the modified wood drying faster and thus exhibiting a better quality.