Through Thermogravimetry Research Articles

Preparation of Zn/Zr-MOFs by microwave-assisted ball milling and adsorption of lomefloxacin hydrochloride and levofloxacin hydrochloride in wastewater

The Zn/Zr-MOFs were synthesized via microwave-assisted ball milling and subsequently characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The thermal stability of the Zn/Zr-MOFs was evaluated through thermogravimetry (TGA). The results demonstrated the exceptional adsorption properties of the Zn/Zr-MOFs towards Lomefloxacin hydrochloride and Levofloxacin hydrochloride. At a concentration of 30 ppm for Lomefloxacin hydrochloride, the addition of 30 mg of Zn/Zr-MOFs material resulted in an adsorption capacity of 179.2 mg•g−1. Similarly, at a concentration of 40 ppm for Levofloxacin hydrochloride, the addition of 30 mg Zn/Zr-MOFs material led to an adsorption capacity of 187.1 mg•g−1. Kinetic analysis revealed that the experimental data aligned well with a pseudo-second order kinetic model. Overall, these findings highlight the significant potential application of Zn/Zr-MOF materials in wastewater treatment.

Construction of energetic metal-organic frameworks based on 5-aminotetrazole

Metal-Organic Frameworks (MOFs) have recently gained prominence as a novel class of energetic materials, owing to their systematic design and the ability to fine-tune properties such as energy content, sensitivity, and thermal stability. In this study, two new MOFs namely Cd(5-AT)3NH2(CH3)2+(1) and Zn(5-AT)(AMP) (2) (5-HAT = 5-aminotetrazole) were prepared under solvothermal conditions using 5-aminotetrazole as the high-nitrogen energetic ligand. X-ray single crystal diffraction analysis revealed that compound 1 possess an ABX3-type perovskite-like structure, whereas compound 2 forms a two-dimensional layer. The high thermal stability of both compounds were confirmed through thermogravimetry (TG) and differential scanning calorimetry (DSC). Their constant-volume combustion heat (ΔcU) was first determined by oxygen-bomb calorimetry and then the standard molar enthalpy of formation (ΔfHo) was calculated. Furthermore, both compounds demonstrated great detonation properties and low sensitivity, showing their potential application as new explosive materials (EMs).

Kinetic and thermodynamic study of composite with jute fiber as reinforcement

In the present work, engineered by compression molding process via a hydraulic press, the A and B composite samples were carried out with 5% and 10% ratio respectively of Ricinodendron heudelotii oil-based alkyd resin in bio-based matrix made of unsaturated polyester using jute fibers as reinforcement material. The samples’ thermal decomposition was performed through thermogravimetry (TG) and derivative thermogravimetry (DTG) analyses. Both composite samples exhibit two stages of decomposition, where the main occurs at 200 - 550°C. Aiming to study and being able to model the thermal degradation of the elaborated composites, finding the kinetic triplets appears the best option to describe the kinetic process undergo by the composites in order to evaluate the performance application of the composites. Two non-isothermal techniques, Flynn-Wall-Ozawa (FWO) and Kissinger have been used to assess the activation energy Ea, and it is found that the apparent activation energy varies with the degree of conversion indicating that both composites decompose with a multiple step mechanism process. The appropriate reaction model for the second stage of decomposition was best suited with Johnson-Mel-Avrami (n<1) model and has been established, allowing us to model thermal degradation behavior of our elaborated composite material and set predictions. The estimated Arrhenius factor values were respectively about A and B composites, 4.12.1015 min-1 and 10.42.1015 min-1, allowing us to set the final equation characterizing the degradation process for the second and main decomposition stage. Finally, as a result of comparison between A and B composites, A appears to be the more thermally stable due to its lower values of Arrhenius pre-exponential factor over the main stage of decomposition and higher calculated the activation energy values.

Investigations into extra-heavy crude oil pyrolysis under non-isothermal conditions: thermal characteristics, kinetics, and thermodynamic parameters

This study comprehensively investigated the pyrolysis characteristics, kinetics, and thermodynamic parameters of extra-heavy oil through thermogravimetry (TG) experiments. The TG results revealed a two-stage pyrolysis process, consisting of light-temperature pyrolysis (LTP) and high-temperature pyrolysis (HTP), in which the HTP was the primary mass loss interval, contributing roughly 53.5% of mass loss from 370 to 500 °C. The pyrolysis kinetics were obtained using Ozawa-Flynn-Wall (OFW) and Friedman methods. The results revealed that the main pyrolysis reaction mechanism shifted from volatilization to thermal cracking while the conversion degree exceeded 0.35. The thermodynamic parameters, including enthalpy (ΔH), Gibbs free energy (ΔG), and entropy (ΔS), were also calculated. The thermodynamic features showed that the pyrolysis process absorbed large amounts of energy to change the main reaction mechanism in the range of α = 0.4–0.6, and altered from an organized to a disordered state due to the disruption of intramolecular structure induced by the formation of coke while the conversion degree exceeded 0.6. These findings have the potential to offer a thorough comprehension of the pyrolysis mechanism of extra-heavy oil.

Kinetic and thermodynamic study of pyrolysis of the hydrolyzed residue of rice straw and husk by subcritical water process using thermogravimetric analysis

AbstractThe use of hydrolyzed rice straw (HRS) and hydrolyzed rice husk (HRH) as feedstock for pyrolysis was evaluated through kinetic and thermodynamic studies. HRS and HRH were obtained from subcritical water hydrolysis (SWH) at different temperatures (180, 220, and 260°C). The Coats‐Redfern method was used to analyze the thermal behavior through thermogravimetry (TG) and derivative thermogravimetry (DTG) curves. TG profiles showed higher decomposition in the range of 250–400°C, especially for rice straw (RS) and HRS (80 wt %). The pyrolysis curves were well predicted by a first‐order reaction model. The kinetic analysis showed a variation in activation energy (EA) between 24.3 to 41.3 kJ mol−1 and 40.4 to 54.7 kJ mol−1 for RS/HRS and rice husk (RH)/HRH, respectively. The enthalpy (ΔH), Gibbs free energy (ΔG), and entropy (ΔS) varied from 25.9 to 39.6 kJ mol−1, 35.4 to 69.6 kJ mol−1, and −64.1 to −6.7 J mol−1 K−1, respectively, for RS/HRS, and 35 to 49.8 kJ mol−1, 43.2 to 79.3 kJ mol−1, and −53.5 to −10.2 J mol−1 K−1, respectively, for RH/HRH. These results showed that the pyrolysis reactivity using HRS is higher than HRH, which indicates the pyrolysis of HRS is more advantageous than HRH.

Thermal stability of levopimaric acid and its oxidation products

Biofuels are renewable alternatives to fossil fuels. Levopimaric acid‒base biofuels have attracted increasing attention. However, their stability remains a critical issue in practice. Thus, there is a strong impetus to evaluate the thermal stability of levopimaric acid. Through thermogravimetry (TG) and a custom-designed mini closed pressure vessel test (MCPVT) operating under isothermal and stepped temperature conditions, we investigated thermal oxidation characteristics of levopimaric acid under oxygen atmosphere. Thin-layer chromatography (TLC) and iodimetry were used to measure the hydrogen peroxides generated by levopimaric acid oxidation. A high pressure differential scanning calorimeter (HPDSC) was used to assess hydroperoxide thermal decomposition characteristics. Gas chromatography-mass spectrometry (GC-MS) was used to characterize the oxidation products. The thermal decomposition kinetics of levopimaric acid were thus elucidated, and a high peroxide value was detected in the levopimaric acid. The decomposition heat (QDSC) and exothermic onset temperature (Tonset) of hydroperoxides were 338.75 J g−1 and 375.37 K, respectively. Finally, levopimaric acid underwent a second-stage oxidation process at its melt point (423.15 K), resulting in complex oxidation products. Thermal oxidation of levopimaric acid could yield potential thermal hazards, indicating that antioxidants must be added during levopimaric acid application to protect against such hazardous effects.

Structural reversible adhesives based on thiol-epoxy vitrimers

This work presents a family of functional adhesives based on covalent adaptable networks (CANs). Low-cost and commercially available monomers, including diglycidyl ether of bisphenol A, pentaerythritol tetrakis (3-mercapto propionate) and dipentaerythritol hexakis (3-mercapto propionate), were cured using a base catalyst to produce highly cross-linked materials. The catalyst selection and the study of the curing reaction were performed using differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR). The catalyst was chosen for better feasibility of industrial production, characterized by short curing times and relatively low temperatures. Thermal stability and thermomechanical properties of the final materials were evaluated through thermogravimetry (TGA) and dynamic mechanical thermal analysis (DMTA), respectively, revealing glass transition temperatures (Tg) higher than 50 °C. Stress relaxation tests were conducted to investigate the vitrimeric behaviour of the polymers, which exhibited an Arrhenius-type dependence of relaxation times on temperature. Importantly, both materials demonstrated impressive creep resistance up to 70 °C, indicating their suitability for use at elevated service temperatures. Tensile and lap-shear tests were also performed, revealing high lap-shear strength values (up to 16 MPa) comparable to those of commercial adhesives. Furthermore, these vitrimers displayed remarkable properties such as shape memory, shape reconfiguration, and self-welding capabilities, underscoring their excellent potential for a wide range of highly demanding applications in industrial production.

Thermo-oxidative behavior and kinetics analysis of light and heavy oils based on TG, DSC, and FTIR

In-situ combustion (ISC), as a time-honored replacement technology for heavy reservoir development, needs to improve its application effect urgently. The oxidation exothermic behavior and reaction activity of heavy oil directly determine the EOR effect of ISC technology during air injection. In this work, the oxidation heat effect and combustion activity of light and heavy crude oils, and the physical properties of their oxidized oils were studied and compared through thermogravimetry (TG), differential scanning calorimetry (DSC), static non-isothermal oxidation and Fourier transform infrared spectroscopy (FTIR). The results indicate that the main reaction pathway of MH light oil is distillation and volatilization under 200 °C, the mass loss is obvious and the heat release is more than that at the high temperature oxidation (HTO) stage. After the full reaction of FC heavy oil at 350 °C, there is still about 30% low temperature oxidation (LTO) left. After the LTO and fuel deposition (FD) stages, heavy oil can produce more coke. MH light oil and FC heavy oil show an obvious mass loss at the stage of LTO and HTO, which is 68.8% and 27.3% (10 °C/min) respectively, the corresponding enthalpies are 3.02 kJ/g and 15.668 kJ/g as well. Between 470 and 500 °C, the endothermic reaction of heavy oil becomes weak, which may relate to the condensation of heavy components such as resins that release heat. The LTO activation energy of light oil decreases with the conversion, and temperature increase can promote the oxidation reaction of active components. The LTO activation energy of heavy oil increases with the conversion, while that in FD and HTO stage increases obviously, which indicates that coke combustion activity is low. The content of C1–C6 in heavy oil decreases from 5.81% to 3.57% with heating rates. The oxidation reaction in the full temperature range can improve the quality of heavy crude oil. The vibration peak at 1707 cm-1 of the MH oxidized oil gets weak, the vibration peak at 1539 cm-1 disappears, and the number of carboxyls, ether groups, aromatic rings, and miscellaneous molecules in the oxidized oil declines. The vibration peak at 3460 cm-1 of the oxidized oil enhances significantly, and the number of carboxyls and hydroxyl molecules increased.

Domain Structures and Temperature Induced Phase Transitions in Perovskite Molecular 3‐Ammonioquinuclidinium‐NH 4 Cl 3

Centimeter-sized perovskite molecular 3-ammonioquinuclidinium-NH4Cl3 (3-AP-NH4Cl3) was grown by slow evaporation method. Through thermogravimetry (TG), differential scanning calorimetry (DSC) and dielectric measurement, a temperature-induced phase transition was found at 146 °C. Stripe domain structures at room temperature were observed by polarized light microscopy (PLM). Domain structure evolution was observed in situ during the temperature-induced phase transition, which further confirms the phase transformation from ferroelectric phase to paraelectric phase.

Synthesis, growth, spectral and computational studies on aminomethylpyridinium trichloroacetate single crystal

The molecular compounds 2-amino-6-methylpyridine and trichloroacetic acid were synthesized in the ratio 1:1 and a single crystal aminomethylpyridinium trichloroacetate (AMPTA) was grown with the base compound 2-amino-6-methylpyridine (2AMP) as a donor and the acid compound trichloroacetic acid (TA) functions as an acceptor. The modes of vibration with the functional group was investigated from the analysis of FTIR spectroscopy. The existence of proton was prognosticated by 1H NMR spectral analysis. The π→π∗ transition shifted to wavelength 310 nm in UV–vis-NIR spectra confirms the emergence of the AMPTA crystal. The percentage of transmittance spectrum showed the suitability of the compound for non-linear optical applications. TG-DTA analysis was done to study the thermal stability and the melting point of AMPTA crystal was assessed through thermogravimetry (TG) and differential thermal analysis (DTA). The density functional theoretical method (DFT) was carried out with the help of the B3LYP/3-21G(d,p) basis set, and the results were compared with the experimental values.

Effect of glycerol on the thermal decomposition behavior of nickel propionate-based precursor

In this work a detailed analysis of the decomposition behavior of nickel acetylacetonato-propionate with and without additive addition was investigated through thermogravimetry (TG) coupled with differential thermal analyses (DTA) and mass spectrometry (MS), while chemical characterization has been carried out with Fourier transform infrared spectrometry (FTIR), X-ray diffraction analyses (XRD). Electron Spin Resonance and UV–vis measurements were performed to confirm whether the complexation of the precursor with additive occurs. The glycerol addition has effect on decomposition behavior of the precursor powder by shifting the main decomposition temperature with more than 100 °C to lower values. Regarding the intermediate decomposition products, they are similar at lower temperatures, while at final decomposition temperatures high exchanges occurs Ni metallic it is fully oxidized in the case of thermal decomposition of the nickel acetylacetonato-propionate precursor, while in the case of the precursor with glycerol addition, metallic nickel is still observed concomitant with NiO phase. The thermal decomposition mechanism of the precursors has been proposed.

Fe-C nanoparticles obtained from thermal decomposition employing sugars as reducing agents

The aim of the work is to present a comparative analysis (structural and magnetic) of Fe-C nanocomposites obtained by the thermal decomposition of sugars (fructose, glucose and sucrose) employing FeCl3 as Fe3+ precursor. The thermal decomposition was followed through Thermogravimetry (TGA) and Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction, High Resolution Transmission Electron Microscopy (HRTEM) and Raman spectroscopy. The results indicate the reduction of Fe3+ under the performed thermal treatments and the achievement at high annealing temperatures of Fe-C nanostructures (coexistence of α-Fe and Fe3C nanoparticles surrounded by a carbon matrix). The magnetic characterization performed by dc SQUID magnetometry, shows an antiferromagnetic response in the initial stages of the decomposition process, and a ferromagnetic behavior linked to the Fe-based nanoparticles. The magnetic induction heating was analyzed through the ac hysteresis loops. Moderate Specific Absorption Rate (SAR) is obtained in Fe-C nanoparticles (~ 70 W/gFe), ascribed to the large nanoparticle size. The combination of porous carbon structure and ferromagnetic response of the Fe-C nanoparticles (i.e. local temperature increase under ac magnetic field) enlarge the emerging applications of these carbonaceous nanocomposites.

Synthesis of poly(2-(methacryloyloxy) ethyl ferrocene carboxylate-co-methacrylic acid)s and their anti-migration and burning rate catalytic properties

A series of copolymers of poly(2-(methacryloyloxy) ethyl ferrocene carboxylate-co-methacrylic acid)s (P(FHEMA-co-MAA)s) were synthesized as burning rate catalysts (BRCs). Their structures were verified using proton nuclear magnetic resonance (1H NMR) and Fourier transforms infrared (FT-IR) spectroscopy. The electrochemical behavior of P(FHEMA-co-MAA)s was investigated by cyclic voltammetry (CV). The CV results indicated that P(FHEMA-co-MAA)s showed redox behavior. Anti-migration test proved that P(FHEMA-co-MAA)s possesses better anti-migration properties than ferrocene (Fc) and 2, 2-bis (ethylferrocenyl) propane (Catocene). The burning rate (BR) catalytic effect of P(FHEMA-co-MAA)s on thermal decomposition of AP was examined through thermogravimetry (TG) and differential thermogravimetry (DTG). P(FHEMA-co-MAA)s were found to have high catalytic effects in accelerating thermal decomposition of ammonium perchlorate (AP).

Preparation of various manganese dioxide composites and their desulfurization performance

The performance of desulfurization materials plays a key role in desulfurization technology. In this study, different types of manganese dioxide (MnO2) composites were prepared to improve desulfurization performance. These composites were characterized intensively via SEM, XRD, XPS, and BET. Desulfurization performance was measured through thermogravimetry (TG), and the desulfurization mechanism of different types of MnO2 composite was investigated. Results showed that the desulfurization performances of MnO2 composites are determined by the combined effects of the materials’ pore structure, specific surface area, active components and Mn valence contents. The desulfurization performances of high specific surface area MnO2 and porous MnO2 were enhanced on account of their excellent physical structures. The desulfurization performance of alkali metal additive LiOH doped MnO2 improved through the addition of active components. The desulfurization performance of bimetallic oxide MnO2/CeO2 improved through the synergistic effect of bimetallic oxides. The desulfurization performance of carrier type MnO2/NaY improved through the dispersion of MnO2 particles. Among the composites obtained, porous MnO2 revealed the best desulfurization performance, this composite demonstrated an average SO2 capture rate of 0.283 gSO2/gmaterial·h within the first hour of reaction, and its SO2 capture capacity was 0.633 gSO2/gmaterial.

Synthesis and characterization of hydrogenated novel AlCrFeMnNiW high entropy alloy

A novel high entropy alloy (HEA) i.e. AlCrFeMnNiW is synthesized via high-energy planetary ball milling with an average crystallite size of 10.37 nm. The morphology study of hydrogenated and dehydrogenated HEA is carried out through Scanning Electron Microscope (SEM). The HEA is charged with hydrogen using inhouse Sievert's Apparatus which results to be maximum hydrogen storage capacity of 0.615 wt% at atmospheric pressure and temperature. The dehydrogenation of the sample is performed through thermogravimetry (TG) at different scanning rate. The crystalline structure (i.e. lattice parameters) and chemical composition of HEA is studied using X-Ray Diffraction (XRD) and Energy Dispersive X-Ray analysis (EDX) respectively. The unit cell volume of as-prepared alloy is estimated as 0.03131 nm3 whereas the average crystallite size as 10.37 nm. It is observed that the unit cell volume is increased by 0.67% and crystallite size decreased by 10.8% upon hydrogenation whereas it is then decreased by 0.2% and increased by 6.7% respectively upon dehydrogenation. Activation energy during hydrogen desorption is found to be −8.161 kJ/mol. The enthalpy and entropy of the mixing are estimated to be −2.645 kJ/mol and 1.793 R J/mol K.

Exploring the electrical and complex optical properties of as-synthesized thiophene-indole conducting copolymers

In this contest, a novel series of random thiophene-indole (Th-In) conducting copolymers have been synthesized through oxidative copolymerization of their monomers in aqueous medium at room temperature using anhydrous ferric chloride (FeCl3) as an oxidant. The structure of as-studied samples have been confirmed through X-ray diffraction (XRD) technique. Field emission-scanning electron microscopy (FE-SEM) ensured the morphology of as-prepared copolymers. The complex optical parameters of the samples have been estimated through ultraviolet-visible (UV-Vis) spectroscopy. The temperature dependence of dc electrical conductivity of the samples have been obtained over a temperature range 303–393 K, which found to be in the range 10−6–10−4 Scm−1 followed Arrhenius relation. The degradation behaviour has been studied through thermogravimetry (TG) and differential thermal analysis (DTA) techniques.

Classification and characterization of bound water in marine mucky silty clay

Bound water has a large impact on physical and chemical properties of clay. The objective of this study was to investigate the contents, types, and physical properties of bound water and provide insights for understanding the thermal behavior and hydration process of the marine mucky silty clay under the control of bound water. An integrated approach incorporating isothermal adsorption, thermogravimetric analysis (TGA), and specific gravity testing were developed to determine the contents and the boundaries of different types of bound water in Qingdao clay and investigate their physical characteristics. Adsorption isotherm can be divided into two phases, which are the formation of strongly bound water and some capillary water under condition of p/ps 0.9. The initial dehydration temperatures of strongly bound water range between 87 and 92 °C in the hydrated clays under condition of p/ps < 0.98. Weakly bound water starts to be released at temperatures near 60 °C and is completely removed at temperatures between 90 and 108 °C. Capillary water and free water are evaporated before 60 °C. The specific gravity of hydrated clay decreases linearly with adsorbed water contents. The volume of hydrated clay, volume of adsorbed water, and thickness of water film approximately linearly increase with adsorbed water contents. Quantitative determination and classification for bound water can be implemented through thermogravimetry (TG) and derivative thermogravimetry (DTG) curves. The physical properties of hydrated clay and bound water film are directly affected by the adsorbed water contents. The results may contribute to environmental and engineering risk assessment.

Evaluation on thermal stability and kinetics of 2,2′-azobis(2,4-dimethyl)valeronitrile in aerobic and anaerobic conditions under isothermal process

We quantified the thermal stability of 2,2′-azobis(2,4-dimethyl)valeronitrile (ADVN) under isothermal conditions through thermogravimetry (TG), differential scanning calorimetry (DSC), and model-free as well as model-fitting methods. We selected two gaseous atmospheres—N2 and air—to observe the thermal degradation behaviors of ADVN with or without O2 by TG. The results showed that when oxygen was present, the mass loss and thermal degradation rate of ADVN decreased because of azoxy compounds production. In addition, the thermal degradation behaviors of ADVN were noticeable at 30 °C, which is close to room temperature. Therefore, storage and transportation of ADVN should be appropriately controlled under low-temperature conditions. Finally, the kinetic behaviors of ADVN were determined using DSC data, model-free, and model-fitting methods under isothermal conditions.

Thermal analysis of ancient ceramics using the microchemical and microstructural alterations of foraminifera

Thermal degradation of planktonic and benthic foraminifera within the coarse wares of Qizlar Qaleh and clay from Khangiran Formation in Kopet Dagh basin, Iran, were examined at different temperature rates. Hyaline and agglutinated tests of foraminifera were investigated through Thermogravimetry (TG), Derivative thermogravimetry (DTG), Fourier Transform Infrared (FTIR) spectroscopy and Scanning Electron Microscope coupled with Energy Dispersive Spectrometry (SEM-EDS) to identify their thermal stability and chemical transformation from 500°C to 1000°C. TG/DTG and FTIR analyses show significant weight loss in the range of 750–800°C and a progressive decrease in the intensity of carbonate bands at 1424, 2514 and 875cm−1 (from 700°C, to 800°C) which indicates the release of CO2. In addition, the chemical characteristics of the agglutinated tests indicate high thermal stability due to their high silicate component. The complete decarbonization of hyaline tests occurred at around 800°C, whereas the agglutinated tests are still preserved at 1000°C. Finally, microstructural and microchemical analysis of foraminifera from the ancient ceramics and Khangiran clay indicated firing temperature of the ceramics at around 700–750°C. The X-ray diffraction (XRD) and a comparative TGA and FTIR analysis of the ceramics and the fired clay samples from Khangiran Formation also show a high intensity of calcite bands, indicating a firing temperature<750°C. This approach provides a new tool for estimating the firing temperatures of ancient ceramics.

Reactive powder concrete reinforced with nano SiO2-coated TiO2

Nano SiO2-coated TiO2 (NSCT) is used to reinforce reactive powder concrete (RPC). The reinforcing mechanisms of NSCT are investigated through thermogravimetry (TG) analysis, X-ray powder diffraction (XRD) analysis, elemental analysis and scanning electron microscope (SEM) observation. The mechanical strengths of the NSCT reinforced RPC (NSCTRRPC) at different curing ages manifest significant increases, especially flexural behaviors. The flexural and compressive strengths of NSCTRRPC at age of 28d achieve increases of 87%/6.69MPa and 12.26%/12.2MPa with respect to RPC without NSCT, respectively. TG analyses suggest that acceleration of cement hydration caused by nucleus effect plays a dominant role in the early days. XRD analyses manifests the NSCT decreases the amount of CH crystals in matrix. This suggests that the NSCT has the pozzolanic effect. In addition, element analysis is indicative that NSCT is uniformly distributed inside the matrix to make the cement matrix more compact, which is in consistent with SEM observations. It is therefore concluded that coating of nano SiO2 at the surface of TiO2 is beneficial for the dispersion of nano fillers in matrix and the pozzolanic effect, thus modifying the microstructures and the mechanical property of RPC.