Ing. Dominik Pilnaj

The objective of this work was to modify a commercially available 3D printer with a syringe extrusion system inspired by clay 3D printing systems and, afterward, to print conductive test samples from prepared pastes. The pastes were prepared by dissolving polystyrene insulation foam in acetone and adding electrically conductive graphite powder in various loadings. The pastes were homogenized by ultrasonication. Subsequently, the test samples were printed and rested overnight for evaporation of the acetone solvent. Cuboid samples were used for the measurement of the sheet resistance and volume resistivity, followed by analyses of thermal properties and microscopy. The samples containing 23 wt.% and 33 wt.% of graphite exhibited a significantly increased electrical conductivity. Benefiting from a simple preparation, these materials, in conjunction with modified syringe-based 3D printing, can be used in many applications where electrical conductivity is required, such as electromagnetic shielding or sensors.

Two types of solder paste, where for each there were three production / expiry dates, were compared on a gas chromatography and evaluated in terms of their application using stencil printing on a copper substrate (OSP surface finish). The number, percentage, and number of macrovoids were evaluated and compared. Altogether, six solder paste samples were tested, for each solder paste, the voids were evaluated using X-ray spectroscopy on 14 pads with a 1206 pad size. Despite the results from the gas chromatography showed the effect of solder paste aging, the voiding of the pastes did not differ significantly and, on the contrary, the percentage representation of voids was the smallest with the oldest solder paste.

Due to electronics miniaturization, the size of voids is becoming comparable to that of solder joints, thereby increasing the risk of reduced reliability. This work presents a novel method of achieving void reduction through preliminary characterization of the flux and, consequently, the proper flux selection and adjustment of the temperature profile during soldering. To validate this approach, five SAC305 solder pastes differing in flux composition were subjected to testing. The flux components were characterized by a gas chromatograph combined with a mass spectrometer (GC–MS) and thermogravimetric analysis (TGA). Subsequently, four temperature profiles differing in the heating rate were employed for reflow soldering of the test boards with components while maintaining the same peak temperature for all profiles. The results of the X-ray computed tomography (XCT) analysis indicated that as the temperature gradient decreased, the number of voids decreased by up to 36%. The decrease in the number of flux residues detected by TGA present at the peak process temperature was also accompanied by a decrease in the void area within the solder joint. Moreover, a comparison between the GC–MS and XCT results revealed that certain flux compounds, such as butylated hydroxytoluene, were found to have a greater impact on void formation than others. The proposed method combining flux characterization by GC–MS and TGA and adjustment of temperature gradient during the soldering process can be an efficient way to reduce voids in solder joints. Additionally, it appears that a lower temperature gradient is generally associated with a lower incidence of voids.

It is well known that the reflow temperature profile has an influence on the thickness of intermetallic layers. The higher the thermal treatment, especially above the melting temperature of solder alloy, the higher the thickness of intermetallic layers. The heating factor (time-temperature integral of temperature profile above the melting temperature) is commonly used for comparison of the heat treatment. This paper deals with a comparison of three different reflow temperature profiles (with three different heating factors: 242, 1061 and 1652 s.K), three surface finishes (Organic Solderability Preservative - OSP, Hot Air Solder Leveling - HASL and Electroless Nickel Immersion Gold - ENIG) of copper soldering pads and two solder pastes with the same composition of solder alloy (Sn96,5/Ag3,0/Cu0,5) but with different flux type (less aggressive - ROL0 and more aggressive - ROL1). The cross-sections of the samples were prepared after the reflow soldering process, followed by analysis by scanning electron microscope and measurement of intermetallic layers thicknesses. Results confirmed that the heating factor significantly influences the intermetallic layers. The highest thickness of intermetallic layers was achieved with the highest value of the heating factor. The surface finish HASL had the highest values of intermetallic layer thicknesses from all used surface finishes, whereas ENIG had the lowest. The higher values of intermetallic layer thickness were observed for the solder paste with a more aggressive flux, ROL1, than for ROL0.

Polypropylene and carbon dioxide were converted into syngas and solid nanostructured carbon particles. A direct current steam plasma torch provided the high enthalpy for the endothermic process. If the plasma process is powered by renewable electricity, it can be an environmentally viable method for waste treatment, energy conversion, and CO2 utilization. The temperature measured on the walls of the reactor was in the range of 1,150 and 1,350 degrees C, but the temperature of the heat source (steam plasma) was around 10,000 degrees C. The gasifying agent (carbon dioxide) was injected into the reactor at two gasification ratios (sub-stoichiometric or abovestoichiometric). The carbon dioxide conversion rate achieved was 98.5 %. The characterization of the produced nanostructured solid carbon (by HRTEM, SEM, XPS, XRD, EDS and GC-MS) confirmed the complete conversion of polypropylene, as no remnants were found in the product. The nanostructured carbon produced can be used for polymer and tire reinforcement and create additional value for the process as a side product of synthesis gas generation from plastic waste and CO2.

An intermetallic layer (IML) between the solder alloy and the soldered surface affects the mechanical and electrical performance of the resulting joints. Numerous studies have explored the possibilities of influencing the IML to achieve more reliable interconnections. However, the type and composition of the used flux, crucial for the proper creation of solder joints, is rarely included as a possible influencing factor. In this article, a comprehensive study on the interfacial microstructure evolution of lead-free SnAgCu solder joints, accounting for the flux type and the temperature of the preheating phase of reflow soldering, where the flux contained in the solder paste becomes active, is presented. In the results, it is shown that the IML of as-reflowed and thermally aged solder joints depends significantly on the flux. The IML activation energy is 57% higher for rosin-based low-activity (ROL)0 flux compared to ROL1 flux. The ROL0 flux, containing fewer active components, also outperforms the ROL1 flux in both the mechanical and electrical properties of the joints. Furthermore, the temperature profiles also show slight differences in measured properties, with the fluxes responding differently to changes in preheating temperature. In the presented results, importance of the used flux on solder joint microstructure is demonstrated.

Recycling lithium-ion batteries (LIBs) is crucial for environmental sustainability and resource conservation. However, current recycling procedures, particularly for smaller battery formats, pose several challenges. With the increasing demands of the circular economy for LIB waste treatment, it is essential to identify and address obstacles associated with concurrent processes. Thus, this study focuses on characterizing and examining the dilemmas of electrochemical discharging of cylindrical LIB cells. It primarily examines the quantity and composition of released battery mass from nickel-aluminium-cobalt (NCA) LIB cells using aqueous discharging via solutions of sodium chloride (NaCl), sodium hydroxide (NaOH), and sodium nitrate (NaNO3) within the 5-30 wt. % range. Additionally, the work monitored several procedure parameters, including the voltage profiles during discharging, the extent of battery contacts and casing damage after discharging, the character and material composition of the obtained battery mass, and the composition of the wastewater obtained after separating the solid product from waste solutions. Consequently, it was determined that the industrial implementation of these procedures, including material leakage and disposal, may incur economic losses of up to 1560 USD/tonne due to metal loss.

To enhance the solderability, highly active fluxes are commonly employed in lead-free soldering. However, there are industry-wide efforts to use less active fluxes to avoid possible issues associated with corrosion processes and minimize subsequent cleaning processes, thereby reducing potential environmentally harmful waste. Therefore, in this study, the effect of the plasma treatment (N2/H2 97:3) on the wettability of the soldered surface (copper connectors) was investigated. Wettability measurements were conducted using SAC305 solder alloy and six different fluxes. The wetting balance test revealed a significant improvement in wetting for all tested fluxes, regardless of their composition. On the other hand, non-wetting occurred when no flux was applied to the plasma-treated surface, attributed to a thin residual oxide layer detected by X-ray photoelectron spectroscopy. Thus, the plasma treatment of the surface supports the flux effect, which cannot be entirely omitted from the soldering process. However, incorporating plasma treatment in the soldering process allows for the use of much less active or even expired fluxes.

Pyrolysis is a promising way of waste transformation into new valuable products. Pyrolytic oil is a mixture of hundreds of compounds and it requires detailed and accurate characterization for future applications. One of the most widely used techniques is mass spectrometry in combination with electron ionization. Tuneable ionization provides benefits including additional structural information and validation of molecular ion due to limited fragmentation at lower energies compared to conventional 70 eV, which provides spectral matches towards libraries. This approach was applied to the compounds identification and group characterization of virgin plastics polyvinyl chloride (PVC), polypropylene (PP), polystyrene (PS), high-density polyethylene (HDPE), low-density polyethylene (LDPE) and their mixture. The use of lower ionization energy was beneficial for distinction of alkanes, iso-alkanes and aromatics. On the contrary to 70 eV, significantly higher fragmentation in branching of iso-alkanes at 12 eV was observed with higher yield of molecular ion also for n-alkane. More than 50 % of detected peaks were identified up to the retention time of icosane. The main analytes of produced pyrolysis oil were monoaromatic (from PVC and PS), alkene/cycloalkane (from PP and mixture). In the case of HDPE and LDPE the main compounds were 1-n-alkenes and n-alkanes. The applied methodology reveals compound group, carbon chain length and degree of unsaturation with higher confidence and success rate compared to traditional nominal mass 70 eV datasets.

3D printing is an extensively used manufacturing technique that can pose specific health concerns due to the emission of volatile organic compounds (VOC). Herein, a detailed characterization of 3D printing-related VOC using solid-phase microextraction-gas chromatography/mass spectrometry (SPME-GC/MS) is described for the first time. The VOC were extracted in dynamic mode during the printing from the acrylonitrile-styrene-acrylate filament in an environmental chamber. The effect of extraction time on the extraction efficiency of 16 main VOC was studied for four different commercial SPME arrows. The volatile and semivolatile compounds were the most effectively extracted by carbon wide range-containing and polydimethyl siloxane arrows, respectively. The differences in extraction efficiency between arrows were further correlated to the molecular volume, octanol-water partition coefficient, and vapour pressure of observed VOC. The repeatability of SPME arrows towards the main VOC was assessed from static mode measurements of filament in headspace vials. In addition, we performed a group analysis of 57 VOC clas-sified into 15 categories according to their chemical structure. Divinylbenzene-polydimethyl siloxane ar-row turned out to be a good compromise between the total extracted amount and its distribution among tested VOC. Thus, this arrow was used to demonstrate the usefulness of SPME for the qualification of VOC emitted during printing in a real-life environment. A presented methodology can serve as a fast and reliable method for the qualification and semi-quantification of 3D printing-related VOC.

Environmental concerns push for a reduction in greenhouse gas emissions and technologies with a low carbon footprint. In the transportation sector, this drives the transition toward electric vehicles (EVs), which are nowadays mainly based on lithium-ion batteries (LIBs). As the number of produced EVs is rapidly growing, a large amount of waste batteries is expected in the future. Recycling seems to be one of the most promising end-of-life (EOL) methods; it reduces raw material consumption in battery production and the environmental burden. Thus, this work introduces a comprehensive pre-recycling material characterization of waste nickel-manganese-cobalt (NMC) LIB cells from a fully electric battery electric vehicle (BEV), which represents a basis for cost-effective and environmentally friendly recycling focusing on the efficiency of the implemented technique. The composition of the NCM 622 battery cell was determined; it included a LiNi0.6Co0.2Mn0.2O2 spinel on a 15 μm Al-based current collector (cathode), a graphite layer on 60 μm copper foil (anode), 25 μm PE/PVDF polymer separator, and a LiPF6 salt electrolyte with a 1:3 ratio in primary solvents DMC and DEC. The performed research was based on a series of X-ray, infrared (IR) measurements, gas chromatography–mass spectrometry (GC-MS), and inductively coupled plasma–optical emission spectrometry (ICP-OES) characterization of an aqueous solution with dissolved electrolytes. These results will be used in subsequent works devoted to optimizing the most suitable recycling technique considering the environmental and economic perspectives.

The popularity of lithium-ion batteries (LIBs) as crucial power sources has increased in recent years. LIBs represent a perspective technology for recycling because they comprise a high portion of valuable metals, such as nickel, manganese, cobalt, or lithium, and other metals, including aluminium, copper, and iron. Battery discharging represents an essential step in end-of-life (EOL) pretreatment, as it reduces the risk of fire or explosion in further processing. As a simple, quick, and inexpensive technique, an electrochemical discharging process via salt-based solutions is preferred for cylindrical cells. Nevertheless, it is necessary to consider the composition of obtained waste products and the possible environmental risks leading to their safe and non-hazardous EOL processing. This work evaluated discharging efficiency and environmental perspective for cylindrical LIB cells, which were treated using NaCl solution. All battery cells were discharged to the safe voltage limit (0.75 V) within 24 hours. Major organic components, including volatile solvents with high toxic hazards, such as carbonic acid esters, methyl salicylate, and propanoic acid esters, were identified in the waste solutions using gas chromatography with mass spectrometry (GC-MS). Moreover, the metal proportion in the solution was determined using inductively coupled plasma - optical emission spectrometry (ICP-OES) analysis; it is recommended to recover metals from the wastewater before EOL or cleaning treatment.

Poly(vinyl chloride) is widely used in the field of electrical engineering as an insulating material. Its properties are significantly dependent on the content of the plasticisers. In this work we identify plasticisers in commercially available insulated electrical wire. We quantify and qualify released hydrogen chloride and qualify volatile organic compounds at enhanced temperatures by thermogravimetric analysis, potentiometric titration, and gas chromatography-mass spectrometry system. Changes in glass transition temperatures and mechanical properties caused by enhanced temperatures are measured by dynamic mechanical analysis. The data show a significant release of hydrogen chloride above 180 °C, which has a significant effect on the mechanical properties.

The ever-increasing requirements for global carbon dioxide CO2 emission reduction decrease the production of new internal combustion engine vehicles (ICEVs). On the contrary, the demand for electric vehicles (EVs) increases along with the number of spent lithium-ion batteries (LIBs). Recycling LIBs seems to be one of the most promising options for end-of-life (EOL) treatment solutions; however, many process effects of currently used battery compounds are still being addressed, e.g., the safety and potential risks of wastewater, battery scrap, or leaks into the air. In this work, the LIB nickel-manganese-cobalt (NMC) cell electrolyte was characterized in wastewater using gas chromatography with mass spectrometry (GC-MS), inductively coupled plasma with optical emission spectrometer (ICP-OES), and the residues of toxic substances bound to nm-μm valuable metal particles in battery scrap were determined by x-ray fluorescence (XRF).