Cathode Ray Tube Research Articles

Calculation of shielding performance of CRT concrete for proton therapy and optimal shielding design of treatment delivery room

Proton therapy is becoming increasingly popular worldwide, and its shielding must be considered. The cathode ray tube (CRT) material is a glass containing heavy metal elements, these materials have become a good choice for the production of radiation-proof concrete. In this study, the ability of concrete containing CRT fragments as shielding materials for proton therapy rooms is evaluated in terms of neutron shielding ability, neutron reflection ability, ambient dose equivalent rate, and induced radioactivity. In addition, this concrete is compared with commonly used ordinary concrete, boron-containing concrete, and barite concrete. The results show that with the increase of CRT content (10%–90%), the transmitted neutron fluence decreases continuously (5.06 × 10−10 – 1.77 × 10−10 cm−2/particle), and the reflection of neutrons gradually increases (2.64 × 10−9 – 3.20 × 10−9 cm−2/particle), resulting in an increased potential to patients. When 50% CRT concrete is used, the ambient dose equivalent rate is below 3.80 μSv/h/nA, and 90% CRT concrete is below 3.11 μSv/h/nA. The trend of radionuclide activity of induced radioactivity from 0 to 60 min after irradiation for concrete with different CRT contents is 2.74–5.38 × 10−3 Bq/cm3, and the maximum photon fluence is 8.13 × 102 cm−2. In conclusion, the optimization model of the three-layer shielding structure of ordinary concrete, high CRT content concrete, and boron-containing concrete is proposed with ambient dose equivalent rate less than 1.88 μSv/h/nA, minimizing the reflected neutrons to which the patient is exposed. This study shows the protection performance of CRT concrete is better than ordinary concrete and barite concrete.

Photosensitive Behavior Studies of the Ba3CaSi2O8:Eu3+ and aCeSiO4:Eu3+Luminescence Material Synthesis

Phosphors made from inorganic oxides and activated with rare earth metals are usedin numerous practical contexts. These include cathode ray tubes, high-efficiency luminouslights, x-ray radiography screens, field emission display panels, and many more.Inorganic phosphor compounds come in a wide variety of forms and have a wide variety ofpracticalapplications. Because of their many advantageous characteristics, including highquantumefficiency, long persistence of the phosphorescence, good stability, and the fact thataluminate-based phosphor is an excellent host material for the lamp industry, aluminatephosphors havea promising future in practical applications. Divalent europium ion dopedsynthetic hexagonal alkaline earth aluminate is an effective luminescence material. Plasmadisplays, field emission displays, fluorescence lamps, etc. all make use of phosphors based onaluminates.Nanophosphors based on the silicates Ba3CaSi2O8 and NaCeSiO4 havebeen produced at 900 ℃using the sol-gel process and doped with Eu3+. Fouriertransform infrared analysis (FTIR), X-ray powder diffraction (XRD), and photoluminescence(PL) techniques were used to examine the bonding, crystalline structure, andphotoluminescence properties of the produced nanophosphors. Europium doped bariumcalcium silicate (Ba3CaSi2O8:Eu3+) and sodium cerium silicate (NaCeSiO4:Eu3+) phosphorsemitted a red glow when exposed to ultraviolet (UV) light. The excitation and emission spectrawere analysed to determine the luminescence parameters of the produced phosphor. Based onXRD analyses, we know that the produced minerals Ba3CaSi2O8:Eu3+ and NaCeSiO4:Eu3+have orthorhombic and cubic structures, respectively, and have sizes of 46.36 nm and 28.57nm. The crystallinity of the finished products was uncovered by XRD analysis. Vacuumfluorescent displays, cathode ray tubes (CRT), safety indicators, luminous paints, fabrics, etc.all benefit from the optoelectronic characterisation of produced phosphors.

Green Conversion of the Hazardous Cathode Ray Tube and Red Mud into Radiation Shielding Concrete.

The present investigation was aimed at the utilization of alternate materials, emphasizing hazardous industrial products (red mud and cathode ray tubes), as constituents of radiation shielding concrete. The usage of these hazardous industrial products improves the sustainability and performance of the radiation shielding concrete. Five concrete blocks were cast and their density, compressive strength, gamma shielding factors, radiation absorption ratio, and transmission factor were explored. For this purpose, gamma-ray shielding measurements were done with the help of an HPGe detector. Mix-1, with zero contents of red mud and CRTs, had the lowest LAC. The LAC results demonstrated that the shielding performance of the current concretes would be better with the increase in red mud and cathode ray tube glass. The Transmission factor (TF) for the prepared concretes with a thickness of 2 cm varied between 11.9–26.1% at 0.06 MeV, while it varied between 4–13% for a thickness of 3 cm. The TF results showed that the composites with a thickness of 2, 3, or 5 cm are good shields against lower energy radiation. The radiation absorption ratio (RAR) for the prepared concretes is high at low energy, suggesting that these new composites can absorb most of the low-energy photons. The RAR results emphasize that the increase in CRTs in the new composites enhanced the radiation shielding features, and when the CRT glass is at a maximum, more attenuation was achieved.

Solution combustion synthesized micron sized yttrium aluminum garnet (Y3Al5O12) powder: A promising feedstock source for plasma spraying

Yttrium aluminum garnet (YAG) is a well-known high-temperature ceramic material that is used in a plethora of applications such as solid-state laser materials, cathode-ray tubes, field emission displays, scintillators, phosphors, electro-luminescent devices, etc. In recent years, plasma-sprayed yttrium aluminum garnet (YAG) has been explored as an alternative ceramic topcoat for thermal barrier coatings (TBCs) as it is known to prevent the oxidation of the bond coat. Also, it possesses high resistance to calcium magnesium aluminosilicate (CMAS) attack compared to conventional yttria-stabilized zirconia (YSZ) TBC topcoat material. In the current investigation, an attempt is made to fabricate plasma-sprayed YAG coating. The flowable powders required for plasma spraying are synthesized by the versatile solution combustion method after optimizing the process with two different fuels. The powders synthesized using hexamine fuel possess blocky angular-shaped particles and very good flowability. The flowability of the powders is correlated to the heat of combustion, adiabatic flame temperature and shape of the particles. The YAG powder synthesized from hexamine fuel is used for plasma spray application as the process results in higher yield and better flowability. The influence of different plasma spray powers (20, 30 and 40 kW) on the phase purity and crystallinity of the YAG coatings is studied using X-ray diffractometry. The influence of three different plasma powers on the microhardness and microstructure of the coatings is explored. The YAG coating plasma-sprayed at 30 kW is relatively a dense coating and exhibits a higher microhardness value of 1342 ± 9 HV at a load of 100 mN. The CMAS resistance of the YAG coatings is also reported.

Tuning the luminescence performance of CdO nanoparticles via Tb2O3 inclusion

The strategy of this work is mainly concentrated on tuning the performance of CdO nanoparticles (NPs) via Tb2O3 addition. Precipitation method is utilized for the NPs synthesis, where Tb2O3 concentrations were 0%, 5%, 10% and 15%. The prepared samples are examined using different analytical techniques. SEM and TEM results showed that Tb2O3 acted as passivation agent for the growth of CdO NPs and annulled particles agglomeration. There is a harmony in crystallites size calculated from XRD and TEM (47–55 nm), whereas, the maximum value is obtained for 5% of Tb2O3. The molecular analysis using FTIR elucidated the stability of the absorption bands for the mixed phase samples comparing with the single one, in agreement with XRD results. The estimated Eg values are ranged within (2.90–2.94) ± 0.02 and are increased slightly with Tb2O3 content. The photoluminescence (PL) spectra using different excitation wavelengths showed two overlapped emission peaks for the mixed phase Tb2O3 - CdO NPs, where the positions and the shape of these peaks appeared to be independent on excitation wavelength. The maximum PL intensity is recorded for the 5% of Tb2O3 using an excitation wavelength of 365 nm. The high intensive of visible emission using different excitation wavelengths suggested the possibility of their use in diverse applications such as light emitting diodes, optical sensor as well as in cathode ray tubes.

Comparison of CRT and LCD monitors for objective estimation of visual acuity using the sweep VEP

PurposeTo investigate the applicability of liquid crystal displays (LCD) as suitable replacement for cathode ray tube monitors (CRT) as stimulator for the sweep VEP for estimating visual acuity.MethodsIn a first experiment, sweep VEPs were recorded in 13 healthy volunteers with best-corrected visual acuity with an LCD and a CRT monitor, respectively. Time-to-peak after stimulus and peak-to-trough amplitudes as well as the visual acuity, estimated using a second-order polynomial and the modified Ricker model, were compared between both monitor types. In a second experiment, sweep VEPs were recorded in six healthy volunteers with two levels of stimulus contrast using artificially reduced visual acuities as well as best-corrected with the same monitors as in the first experiment and additionally, a modern LCD gaming monitor with a response time of 1 ms. Time-to-peak after stimulus and peak-to-trough amplitudes were compared between the different combinations of monitors and contrasts. Finally, visual acuities estimated using the modified Ricker model were compared to subjective visual acuities determined using the Freiburg Visual Acuity and Contrast Test (FrACT).ResultsIn the first experiment, the time-to-peak after stimulus presentation was statistically significantly delayed for LCD displays (mean difference [confidence interval]: 60.0 [54.0, 65.9] ms; t(516) = 19.7096, p < 0.0001). Likewise, peak-to-trough amplitudes were statistically significantly smaller for the LCD stimulator, however, not clinically relevant (mean difference [confidence interval]: − 0.89 [– 1.59, − 0.20] µV; t(516) = − 2.5351, p = 0.0115). No statistically significant effect of the monitor type on the estimated visual acuity was found for neither method, second-order polynomial, nor the modified Ricker model. In the second experiment, statistically significant delays of the time-to-peak after stimulus onset were found for all combinations of monitor and contrast compared to the CRT monitor. A statistically significant, but not clinically relevant, difference of the peak-to-trough amplitudes was only found between the CRT monitor and the LCD gaming monitor (mean difference [confidence interval]: 2.6 [1.2, 4.0] µV; t(814) = 4.66, p < 0.0001). Visual acuities estimated from LCD stimulation significantly underestimated the subjective visual acuity up to 0.2 logMAR using the conversion formula of the first experiment. No statistically significant difference was found when using conversion formulas adjusted for each combination of monitor and contrast.ConclusionsBased on the results of this study, LCD monitors may substitute CRT monitors for presenting the stimuli for the sweep VEP to objectively estimate visual acuity. Nevertheless, it is advisable to perform a calibration and to collect normative data of healthy volunteers using best-corrected and artificially reduced visual acuity for establishing a conversion formula between sweep VEP outcome and the subjective visual acuity before replacing a CRT with an LCD stimulator.

Urgency of technology and equipment upgrades in e-waste dismantling base: Pollution identification and emission reduction

Recycling of electronic waste (e-waste) and inevitable pollution under current technology have always been a concern of people. Generation and release of pollutants in the recycling process of e-waste are closely related to processing technology and equipment. In this paper, the pollution characteristics of different functional areas and critical processing units in formal e-waste dismantling base have been studied systematically and comprehensively. The results showed that the overall pollutants concentration in crushing workshop and cathode ray tube (CRT) monitor disposing workshop are much higher than other functional areas. Screen-cone glass separation for CRT monitor was the processing unit with the greatest exposure risk and the hazard index (HI) of Pb was 4.60. Pollutant emission factor of the main processing units was calculated and the waste printed circuit board (WPCB) crushing was the most polluted unit. Appropriate improvements in technology and equipment can effectively reduce the generation and release of pollutants. Some reasonable prospects about intelligent equipment and special technologies were proposed for e-waste disposal. All the results provided theoretical and data support for pollution control and technology upgrade of the formal e-waste dismantling base.

Cathode ray tubes glass wastes used for vitrification of iron oxide rich waste resulted from the groundwater treatment

Abstract This paper presents a new solution to use the cathode ray tube glass wastes for iron oxide rich waste vitrification. The obtained glass-ceramics, synthesized at three heat treatment temperatures: 800, 900 and 1000 °C were characterized in terms of the effect of the CRT waste glass addition upon the dimensional stability, apparent porosity and density, chemical stability and lead barium and iron ions retention capacity.

Performance of fly ash-based geopolymer mortars with waste cathode ray tubes glass fine aggregate: A comparative study with cement mortars

Utilization of waste cathode ray tubes (CRT) glass as aggregates in the production of ordinary Portland cement (PC) concretes is a sustainable recycling method. However, the high potential of alkali-silica reaction (ASR) degradation puts a limit on the recycling rate of CRT glass. Accelerated mortar bar ASTM C1260 test was employed in this study to differentiate the performance of PC and fly ash-based geopolymer mortars with CRT glass fine aggregate. The results showed that sharp ASR expansion occurred in the PC mortars resulted in great damage to the structure integrity, and consequently a distinct compressive strength loss from 45.1 MPa to 20.6 MPa over time of curing up to 28 days. In comparison, the geopolymer mortars were less susceptible to the ASR degradation, which even exhibited slight shrinkage (−0.057%) at the tested age of 14 days. Due to the deficiency of calcium in the matrix, more flowable ASR gel was formed in the mortar without causing destructive expansion. The lead (Pb) leaching and radiation shielding properties of geopolymer mortars were also tested. The compact pore structure was helpful in restricting the Pb leaching from the CRT glass. The Pb immobilized in mortars effectively enhanced the capacity of radiation shielding. This highlights the potential applications of geopolymer mortars in various radiation shielding constructions.

Optical properties, elastic moduli, and radiation shielding performance of some waste glass systems treated by bismuth oxide

This work reported on the optical properties, elastic moduli, and shielding performance, against charged particles and neutrons, of some waste glass systems, cathode-ray tubes (CRTs), described by (100-x) waste CRTs – xBi2O3 (where x = 0, 10, and 20 mol. %). The synthesis, chemical, and optical features of these glasses were experimentally determined. The well-known Makishima-Mackenzie Model (MMM) was applied to evaluate the elastic properties. The shielding performance of the studied glass specimens against charged particles is evaluated via two fundamental factors namely stopping power and particle range. Such factors are systematically calculated by employing SRIM, ESTAR, PSTAR, and ASTAR programs. Further, the shielding performance of the studied glass specimens against neutrons is evaluated via removal cross section. We found that all elastic moduli decrease as Bi2O3 replaces waste CRTs in the glass network. Moreover, The Σ_R of the glasses follows the trend: CRT-Bi0 (Σ_R=0.0891 cm−1) > CRT-Bi10 (Σ_R=0.0867 cm−1) > CRT-Bi20 (Σ_R=0.0850 cm−1). It is also clear that introducing Bi2O3 into the waste CRTs glass system may appear very beneficial for improving parameter-n, however, higher amounts in the dopant may cause conductive behavior in the glass network on the basis of parameter-M.

Evaluation of the novel Blue Emitting Phosphor with High Thermal Stability and High Color Purity for Solid State Lighting Applications - Ca2MgSi2O7: Eu2 +

This study deals with the new blue release LED phosphor activated by Eu2+. The luminescence properties of blue-emitting phosphor di-Calcium magnesium di-Silicate (Ca2MgSi2O7) doped with europium Eu2+are extensively investigated. This phosphor is produced by the high-temperature solid-state reaction method. The phase structure and crystalline size, surface morphology and elemental analysis were investigated by X-ray diffraction technique (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDX). The optical properties are investigated by photoluminescence (PL) properties. Phase structure of Ca2MgSi2O7: Eu2 + is a carbonite-type structure belonging to tetragonal crystallography with the space group P4̅21m; this structure forms a member and layered compound in the Myelite group. The surface of the prepared phosphors is not detected uniformly and the particle distribution is within the nanometer range. EDX ensures components of Eu2 + doped Ca2MgSi2O7 phosphor. Under UV induction, the main emission peak appeared at 470 nm. This emission peak is attributed to the typical emission of Eu2+ due to the 4F9/2 → 6H15/2 transition. The blue light-emitting properties and excellent light response of these silicate phosphors make them suitable for photonic applications and open new avenues for solid-state lighting, cathode ray tubes, fluorescent lamps and scintillators etc. The phosphor system has been researched as a new candidate for phosphor-converted white light-emitting diode (LED) applications.

Progress of Backlight Devices: Emergence of Halide Perovskite Quantum Dots/Nanomaterials

The technology behind the display is becoming ever more prevalent in our daily lives. It has many applications, including smartphones, tablets, desktop monitors, TVs, and augmented reality/virtual reality devices. The display technology has progressed drastically over the past decade, from the bulky cathode ray tube to the flat panel displays. In the flat panel displays, the liquid crystal display (LCD) and organic light-emitting diodes (OLEDs) are the two dominant technologies. Nevertheless, due to low stability and color tunability, OLEDs remain behind the LCDs. The LCD screen has a backlight, usually a white LED, which comprises a blue LED covered with a red and green enhanced layer (color-converting layers). Although InP/CdSe QDs attracted more attention due to their solution processability and better color gamut than the previous technologies, the complexity of their synthesis was still an obstacle to their commercialization. Later, the emergence of perovskite with highly intense and tunable PL emission, high color purity, and low-cost synthesis route attracted the attention of display researchers. Owing to the relatively higher performance of perovskite quantum dots (PQDs) than that of bulk (3D) perovskite in backlit display devices, these PQDs are being used for high color contrast and bright display devices. Furthermore, the color gamut for PQDs was observed as 140% of the NTSC standard, that is, close to that of the commercial OLED devices. In this review, we have discussed the progress of display technologies with a clear classification of the pros and cons of each technology. Also, the application of perovskite QD/nanomaterials in LCD backlit devices has been discussed, and the future direction of further improvement in their stability and performance has been listed.

Facile functionalization of YVO4:Eu3+: From nanoparticles to luminescent PMMA nanocomposites for radiation detectors

YVO4:Eu3+ is a luminescent material that has been widely used in cathode ray tubes and plasma display panels. Nowadays, different applications are being explored. Fiber-optic Dosimetry (FOD) is an alternative to traditional dosimetry systems for radiotherapy treatments. Although some published results have demonstrated the potential of using YVO4:Eu3+ as nanometer powder for FOD systems, none of them tend to improve its tissue equivalence, a significant limitation. One possible solution could be to disperse the NPs in a tissue-equivalent polymer matrix, like Poly Methyl Methacrylate (PMMA). Consequently, YVO4:Eu3+/PMMA nanocomposites were developed using NPs synthesized according to a combustion method previously reported. This work focuses on studying two different NPs functionalization strategies. One of them involves the synthesis of a SiO2 shell and a posterior treatment with Oleic Acid (OA). The other involves the use of a silane (3-(Trimethoxysilyl)propyl methacrylate, TMSPM) as a coupling agent. Both strategies allow the surface modification of NPs. The study of luminescence properties of NPs showed no significant changes between both functionalized NPs related to Eu3+ spectrum characteristic peaks. However, YVO4:Eu3+@TMSPM has better performance (the reduction in YVO4:Eu3+@TMSPM is about 15%, while in YVO4:Eu3+@SiO2@OA is 62%). On the other hand, functionalized nanoparticles were used to develop polymeric nanocomposites (PNCs) by in situ polymerization of Methyl Methacrylate using a cyclic triperoxide as initiator. Functionalized NPs were characterized by Fourier Transform Infrared Spectroscopy, Transmission Electron Microscopy, Dynamic Light Scattering, Thermogravimetric Analysis, and luminescence measurements. Films were obtained by dissolution of the PNCs, and their luminescent properties were also studied. Results indicate that although the strategy that involves the silica shell plus OA is better in terms of cover density, the TMSPM promotes a better dispersion on the polymer matrix.

Market competition, technology substitution, and collaborative forecasting for smartphone panels and supplier revenues

Market competition coupled with technology substitution concurrently drive rapid progress and revolution of panel displays. Today, display technology has evolved from cathode ray tube (CRT), plasma display panel (PDP), liquid crystal display (LCD), organic light emitting diode (OLED), to mini/micro LED (MLED). Although technical characteristics including intensity, contrast, and duration have been significantly enhanced, it is still difficult for global leaders to forecast product sales because of intensive price variations and dynamic technology evolution. This research presents a novel framework to achieve the following goals: (1) Sales forecast for upstream panels is linked to demand for downstream consumer products, (2) Market competition between the top vendors, Samsung, LGD, and BOE, is included to reveal managerial insights, and (3) Technology substitution between OLED and LCD is captured in smartphone panels to estimate stable equilibriums. Experimental findings show the inclusion of smartphones, tablets, laptops, monitors, and flat TVs can significantly improve the performances of sales forecasting. Meanwhile, Samsung and LGD are mutually independent but LGD suffers from the existence of BOE. Lastly, technology substitution between OLED and LCD reveals global OLED shipments are expected to grow by 12.54% while Samsung’s OLED revenues only increase by 3%.

Recycling potential of cathode ray tubes (CRTs) waste glasses based on Bi2O3 addition strategies

Cathode-ray tubes (CRTs) from computer monitors and television sets are considered as one of the main sources of waste materials worldwide. Therefore, a new application for such out of use materials is required to solve the relatively huge amount of this waste. In this paper, the popular melt-quench technique was used to synthesis glass samples with the structure: xBi2O3–(100-x) waste CRTs (where x = 0, 10 & 20 wt%) and designated as CRT-Bi0, CRT-Bi10, and CRT-Bi20 accordingly. The physical, structural, optical and radiation absorption competence of the glasses were investigated. The XRD analysis of the glasses reveals an amorphous structure while the mass density increased linearly with the Bi2O3 content of the glasses from 2.86 to 3.08 g/cm3. The optical absorbance of the glasses initially increased and later declined in the visible region as the weight fraction of Bi2O3 increased. The direct optical bandgap Eg values were found to be 3.26, 2.72, and 2.64 eV whereas the indirect Eg values were equal to 3.15, 2.30, and 2.26 eV for CRT-Bi0, CRT-Bi10, and CRT-Bi20, respectively. The gamma-ray interaction parameters of the glasses obtained through FLUKA simulations and XCOM computation showed that mass attenuation falls within the range 0.6991–0.0256, 1.1426–0.0276, 1.5860–0.0301 cm2/g for photon energy range 0.1–10 MeV. Generally, the computed gamma ray interaction quantities show that the gamma ray shielding ability of the CRT-Bi glasses follows the order: CRT-Bi0 < CRT-Bi10 < CRT-Bi20. This order is conserved in the computed interaction cross sections for thermal (25 meV) neutrons. On the other hand the fast neutron removal cross section follows a reverse order with values of 0.0891 cm−1, 0.0867 cm−1, and 0.0850 cm−1 for weight fraction of Bi2O3 from 0 to 20 wt%. The comparison of the gamma–ray attenuation capacity of the CRT-Bi20 with common shielding materials reveals good potential for shielding application. Out of use CRT glasses may thus be recycled for use as radiation shielding glasses as described in this study for gamma radiation protection applications.

EZ Mechanical TV: A new twist on the oldest type of television display [Hands On

Before flat screens, before even cathode-ray tubes, people watched television programs at home thanks to the Nipkow disk. Ninety years ago in places like England and Germany, broadcasters transmitted to commercially produced black-and-white electromechanical television sets, such as the Baird Televisor, which used these disks to produce moving images. This early programming established many of the formats we take for granted today, such as variety shows and outside broadcasts.

Video Games as a Teaching Material

The paper deals with the theory of the application of video games in teaching discuss the advantages and disadvantages of using video games as a teaching tool, as well as to raises some additional issues that require further consideration of the use of video games in the classroom. The cathode ray tube amusement device (patent US2455992A) is at the start of its ninth generation of technology. All current knowledge, skills, and innovations of the current age of civilization are united in the creation of such a device and medium when it reproduces for entertainment. Certainly, each of these media, of any kind and how much content, of which there are already more than a million (as shown by digital video game stores Steam, GOG, Google store, PlayStation network), carries a certain amount of data, all kinds of knowledge of our civilization. As video games are popular with all ages, the idea of using them for education and in-classroom automatically arises. This paper is an overview of theoretical considerations of various aspects of the application of video games in the teaching of various authors who have researched this field.

Sustainable Alkali-Activated Slag Binders Based on Alternative Activators Sourced From Mineral Wool and Glass Waste

In the present study, four different locally available waste glass materials (bottle glass-BG, glass wool-GW, stone wool-SW and cathode-ray tube glass-CRTG) were treated with hot concentrated potassium hydroxide (KOH) in order to obtain alternative alkali activators (AAAs). We evaluated the suitability of the solutions obtained for use as AAAs in the production of AAMs. AAMs were prepared using electric arc furnace slag and selected AAAs with a higher content of dissolved Si. We evaluated the performance of the AAMs in comparison to that of slags activated with KOH or potassium-silicate (K-silicate). The compressive strength of the AAMs prepared with KOH-based AAAs were high when Si and Al were simultaneously abundant in the AAA (9.47 MPa when using the activator sourced from the CRTG), and low with the addition of KOH alone (1.97 MPa). The AAM produced using commercial K-silicate yielded the highest compressive strength (27.7 MPa). The porosity of the KOH-based AAM was lowest when an alternative BG-based activator was used (24.1%), when it was similar to that of the AAM prepared with a K-silicate. The BG-based activator had the highest silicon content (33.1 g/L), and NMR revealed that Si was present in the form of Q0, Q1 and Q2. The concentrations of toxic trace elements in the AAAs used for alkali activation of the slag were also determined, and leaching experiments were performed on the AAMs to evaluate the immobilisation potential of alkali-activated slag. In the SW AAAs the results show acceptable concentrations of trace and minor elements with respect to the regulations on waste disposal sites, while in the activators prepared from BG, CRTG and GW some elements exceeded the allowable limits (Pb, Ba, Sb, and As).

Electrical Properties of the Carbon Nanotube-Reinforced Geopolymer Studied by Impedance Spectroscopy.

Geopolymers, recognized as an ecological alternative to cement concrete, are gaining more and more interest from researchers and the construction industry. Due to the registrable electrical conductivity, this material also attracts the interest of other fields of science and industry as a potential functional material. The article discusses the used geopolymer material, created on the basis of metakaolin and waste Cathode Ray Tubes (CRT) glass, reinforced with ultra-long in-house carbon nanotubes (CNT), in the context of its use as a smart material for Structural Health Monitoring. Long in-house made carbon nanotubes were added to enhance the electrical conductivity of the geopolymer. The impedance spectroscopy method was applied to investigate the conductive properties of this material. The paper shows the microscopic and mechanical characteristics of the materials and presents the results of promising impedance spectroscopy tests.

Past Forward

Presents a brief description of Karl Ferdinand Braun" cathode-ray vacuum tube that is able to visually capture the oscillations in electrical circuits.