Thermal Processing History Research Articles

Recovery Cu ad Ce from copper slag by using flotation and chemical methods

Slag, which is now considered as a secondary source, attracts attention due to the metallic values they contain. Copper slags having economical operating grades in terms of Zn, Cu, Ce, Ni, Co, Mo, and V show complex mineralogy due to its thermal processing history. Various methods for the recovery of copper and other precious metals from this byproduct have been studied, and there are many operating flotation plants in industrial scale. However, in cases where physical or physo-chemical mineral processing methods are not sufficient, hydrometallurgical methods are applied. In this study, flotation was applied to copper slag with 0.9% Cu grade. Copper recovery and concentrate grade were found as around 40 and 22.7% Cu, respectively. Further, metal extractions were examined by conducting direct leaching tests. Gel formation was observed, when H2SO4was used in the leach process, therefore, the leach parameters were investigated using HCl. Cu and Ce extractions of around 70-80% were reached as a result of a test performed for 2 hours with the addition of 25 g/L H2O2 at a rate of 20-25% solids and 300 g/L HCl concentration. When the relationship of dissolved metals with each other wasexamined, dissolution behavior of Cu and Ce was quite similar to Al dissolution (R2=0.9).

Microfiltration of buttermilk: Partitioning of proteins and modelling using a resistance-in-series model

The performance of microfiltration ceramic membranes was investigated in terms of protein fractionation efficacy and permeate flux when treating skimmed (0.3% fat) buttermilk. Tests were performed with a 0.1 μm alumina membrane at a transmembrane pressure of 0.2 MPa and a crossflow velocity of 6.3 m s−1. Modelling of the flux was performed using the resistance-in-series model (RIS), combining fouling resistances due to concentration polarisation, adsorption and cake formation. The RIS model was appropriate to describe the main fouling mechanisms with high fitting accuracy (R2 > 0.93). The predominant fouling mechanism was cake layer formation followed by adsorption. The polynomial correction of the exponential growth of mass deposited on the membrane surface was proposed. The function with polynomial correction accurately fit experimental data (R2 = 0.99). Moreover, the thermal processing history of buttermilk resulted in selective transmission of α-LA. However, further studies are required to enhance the efficiency of buttermilk fractionation.

Calibration of Raman bandwidth in large Raman images using a mercury–argon lamp

AbstractRaman imaging has proven to be an important tool in the analysis of astromaterials. Raman imaging can describe the composition and mineralogy of astromaterials in a nondestructive manner preserving precious samples for additional study. Raman bandwidth is a common spectroscopic marker used to elucidate information such as composition, latent strain, and thermal processing history. The observed Raman bandwidth of a sample is a result of a convolution of the true Raman lineshape and the spectrometer's slit function. Thus, to compare Raman bandwidths across spectra and instruments, one needs to calibrate the Raman spectrum to account for effects of the slit function. Astromaterials are heterogeneous requiring the collection of large Raman images for adequate sampling. It is well known that the wavenumber calibration of an instrument drifts with time throughout Raman image collection. Here, we find that the spectrometer slit function also varies with time and laboratory temperature throughout Raman image collection. We utilize a mercury–argon (Hg–Ar) lamp integrated into our Raman microscope in a novel manner to calibrate the bandwidth in each Raman spectrum within our Raman image. We can do this because the narrow Hg–Ar lamp emission lines approximate the spectrometer slit function for each Raman spectrum allowing for the calculation of the true Raman bandwidth from each Raman spectrum within the Raman image. Our technique allows for the comparison of Raman bandwidth throughout a Raman image and between Raman images/spectra collected using different instruments, facilitating scientific analyses that are reproducible across multiple laboratories.

Microstructural origin of the outstanding durability of the high nitrogen bearing steel X30CrMoN15-1

The high nitrogen bearing steel X30CrMoN15-1, marketed under commercial names such as Cronidur30, VC444, NitroMax and N360, is well-known for its outstanding rolling contact fatigue and corrosion properties. More importantly, there are no reports about failure by white etching cracks for this alloy, although this premature failure mode is frequently observed in conventional high carbon bearing steels. To understand the origin of this superior performance, we analyze in the current paper its microstructure prior to rolling contact fatigue by means of scanning electron microscopy, atom probe tomography and nano-indentation, and relate this to its thermal processing history. The origin of the exceptional white etching crack resistance of this alloy is rationalized in terms of the mechanical and thermodynamic stability of the precipitates, the different grain boundary segregation behavior between nitrogen and carbon as indicated by the atom probe results, and the cleanliness of the steel.

Telescope Observations of Interstellar and Circumstellar Ices: Successes of and Need for Laboratory Simulations

AbstractIces play a key role in the formation of simple and complex molecules in dense molecular clouds and in the envelopes and protoplanetary disks surrounding young stars. Some fraction of the interstellar ices may become building blocks of comets, and thus be delivered to the early Earth. Laboratory simulations have proven to be crucial in the derivation of ice abundances, in quantifying reaction rates on cold grain surfaces, in determining the thermal and energetic processing history of the ices, and in understanding the interaction between the ices and the underlying refractory grain surfaces. In this invited topical paper I will review possible ways forward in improving our knowledge of the composition of the ices, as many signatures in the interstellar spectra are still poorly identified. I will also emphasize the observed importance of thermal processing of the ices (crystallization, segregation), which likely affects the chemistry after the initial dominance of grain surface reactions. Continued laboratory work is warranted in view of the upcoming observational data from, for example, the James Webb Space Telescope (JWST), which is ideally suited for ices studies. For an exhaustive review on this topic I refer to Boogert, Gerakines & Whittet (2015).

Infrared thermal processing history of a Ti-based bulk metallic glass matrix composite manufactured via semi-solid forging

A method for using non-contact infrared thermal imaging for determining the processing history of bulk metallic glass matrix composites (BMGMCs) during semi-solid forging is presented. The technique allows for the first estimations of the relevant parameters associated with semi-solid forging, including the heating profile, forging temperatures, cooling rates, and formability parameters. The processing parameters are correlated with microstructure and a new forging viscosity estimation is developed and compared with other techniques. The research offers a new strategy for thermal measurements that is widely applicable to other manufacturing processes.

Effect of the Manufacturing Process on the Texture and the Fraction of Stress-induced Martensite in an Fe-Mn-Si-Cr-Ni Shape Memory Alloy

Fe-Mn-Si based alloys exhibit the shape memory effect (SME) through a γ(FCC) ↔ ɛ(HCP) stress-induced martensitic transformation. Studies carried out with single crystals have shown that the extent of shape recovery depends on the crystal orientation: it is nearly absent if the stress acts along the [001] direction and almost perfect when applied in the [414] direction. Therefore, certain crystallographic textures in polycrystals may contribute to better shape recovery with less applied stress. On the other hand, the texture is a consequence of the thermal and mechanical material processing history. This study analyzes how the particular forming process and the consequent texture development affects the amount of stress-induced ɛ martensite in an Fe-15Mn-5Si-9Cr-5Ni shape memory alloy. Besides determining the quantity of martensite produced, we measured the critical transformation temperatures and analyzed the effect of the manufacturing procedures on the SME properties.

Rheological studies of thermotropic phase transitions in cationic vesicle suspensions: Instantaneous “jamming” and aging behavior

Cationic double-tailed surfactants exhibit a rich thermotropic phase behavior. Here, we examine the effect of thermal gradients and processing history on the rheology and microstructure of concentrated multilamellar vesicle (MLV) suspensions made from a double-tailed cationic surfactant (diC18:0 DEEDMAC), whose bilayers are in the crystalline (solid) state at room temperature. The rheological properties of the MLV suspensions are found to be strongly dependent on the thermal behavior of the constituent bilayer with the visco-elastic moduli exhibiting a nonmonotonic variation with temperature, initially increasing by 1–2 orders of magnitude at an intermediate temperature, before rapidly decreasing at higher temperatures. Furthermore, when subject to a contraction flow through an extruder, above the main phase transition temperature of the bilayers, the suspensions instantaneously transform into a “jammed,” glassy-state at the extruder outlet. The glassy dispersions behave like stiff gel-like materials, having visco-elastic moduli that are several orders of magnitude higher than their unextruded counterparts. We probe mechanisms leading to the formation and subsequent aging of the jammed suspensions and show that the microstructural evolution of the extruded “gels” on aging is qualitatively different from that of the unextruded suspensions.

Thermal Processing History and Resulting Impact Response of a Hot-Formed Component with Tailored Properties – Numerical Study

The impact modeling of a hot-formed component with tailored mechanical properties is studied to understand the influence of the thermal processing history and how the final properties of the component will affect its impact response. This paper presents a numerical study of the forming and quenching process and subsequent impact simulations. The processing simulations serve to predict the final microstructure and hardness distribution within a lab-scale B-pillar component that is processed using a tool with separate heated and cooled regions. A remapping algorithm is used to translate the results of the forming simulation to the impact simulation. A strain-rate sensitive material model is applied to model the response of these tailored microstructures during impact events. A comparison between a component that is fully hardened and a tailored component with regions of lower strength but increased ductility is presented in this work. Simulations that do not consider the onset of fracture predict superior peak impact load and energy absorption of the fully martensitic component due to its higher overall strength. However, the bainitic regions within the tailored component exhibit much higher ductility. Current work is addressing the introduction of failure criteria into simulations of tailored hot stamped components under impact loading for which the tailored component is expected to demonstrate superior resistance to cracking relative to the fully hardened component.

Influence of two liquid crystalline polysiloxanes with different average molecular weight as new β-nucleator on crystallization structure of isotactic polypropylene

Two liquid crystalline polymers (LC-N1 and LC-N2) with different average molecular weight were designed and synthesized as a new β-nucleator in isotactic polypropylene (iPP). The main aim of this work was to investigate the influence of LC-N1 and LC-N2 on the crystallization structure and β nucleating activity of the iPP with wide angle X-ray diffraction and polarized optical microscopy. The β nucleation activity not only depended on the nucleator content, mesogenic molecular structure, and thermal processing history, but also on average molecular weight of the liquid crystalline polymers. LC-N1 or LC-N2 has been found to be an effective β-nucleator for the iPP. The experimental results indicated the relative content of β-crystal first increased and then decreased with increasing the nucleator content or crystallization temperature. The addition of LC-N1 or LC-N2 could provide a large number of nuclei, enhance the crystallization rate, reduce the spherulite size, and lead to a more uniform morphology; moreover, the colorful β-crystal was also induced. In addition, LC-N2 with higher average molecular weight is more effective than LC-N1 in inducing β heterogeneous nucleation under same crystallization conditions.

Influence of processing history on water and salt transport properties of disulfonated polysulfone random copolymers

Disulfonated poly(arylene ether sulfone)s are high glass transition temperature polymers, and their water and salt transport properties depend sensitively on thermal processing history. In this study, films of a 32 mol% disulfonated poly(arylene ether sulfone) random copolymer (BPS-32), polymerized in the potassium counter-ion form, were acidified using solid state and solution routes. The resulting acid counter-ion form materials were then converted to sodium, potassium, and calcium counter-ion forms via ion exchange. Additionally, several films were subjected to various thermal treatments in the solid state. Water uptake as well as water and NaCl permeability of these BPS-32 films were measured. Acidification via immersion of BPS-32 films in boiling sulfuric acid solution increased water uptake, and water and salt permeability increased. Exposure of samples to elevated temperature also influenced transport properties. For example, immersing BPS-32 films in boiling water for 4 h increased water sorption by 50%, water permeability by 2.3 times, and NaCl permeability by 8 times. The counter-ion form of the sulfonated polymer influenced the polymer’s transport properties, but these effects were weaker than the effect of thermal treatment. Generally, the BPS-32 samples prepared with different processing histories followed a trade-off between water/salt permeability selectivity and water permeability. These results suggest that, like many other glassy polymers, thermal processing history influences small molecule transport in these materials.

Thin ferroelectric poly(vinylidene fluoride-chlorotrifluoro ethylene) films for thermal history independent non-volatile polymer memory

In this study, we investigated the molecular and microstructures of thin poly(vinylidene fluoride-chlorotrifluoro ethylene) (PVDF-CTFE) copolymer films with three different CTFE compositions of 10, 15, 20wt% with respect to PVDF in relation with their ferroelectric properties. All PVDF-CTFE annealed at 130°C showed consecutive TTTT trans conformation with β type crystals while films molten and re-crystallized from a temperature above their melting points exhibited α type crystals with characteristic TGTG conformation. Microstructures of the films treated with the two different thermal histories also supported the formation of β and α type crystals with hundreds of nanometer scale sphere caps and micron level spherulites, respectively. Interestingly, PVDF-CTFE films with both α and β type crystals gave rise to relatively high remnant polarization of approximately 4μC/cm2 in metal/ferroelectric/metal capacitors regardless of the composition of CTFE. The ferroelectric polarization of a PVDF-CTFE film independent of thermal processing history allowed a wide processing window and easy fabrication protocol, resulting in a non-volatile ferroelectric field effect transistor memory which exhibited saturated hysteresis loops with the current ON/OFF ratio of approximately 103 at ±60V sweep and reliable data retention.

Rapid Fingerprinting of Milk Thermal Processing History by Intact Protein Mass Spectrometry with Nondenaturing Chromatography

Thermal processing of foods results in proteins undergoing conformational changes, aggregation, and chemical modification notably with sugars via the Maillard reaction. This can impact their functional, nutritional, and allergenic properties. Native size-exclusion chromatography with online electrospray mass spectrometry (SEC-ESI-MS) was used to characterize processing-induced changes in milk proteins in a range of milk products. Milk products could be readily grouped into either pasteurized liquid milks, heavily processed milks, or milk powders by SEC behavior, particularly by aggregation of whey proteins by thermal processing. Maillard modification of all major milk proteins by lactose was observed by MS and was primarily present in milk powders. The method developed is a rapid tool for fingerprinting the processing history of milk and has potential as a quality control method for food ingredient manufacture. The method described here can profile milk protein oligomeric state, aggregation, and Maillard modification in a single shot, rapid analysis.

Stability of Retained Austenite in High-Al, Low-Si TRIP-Assisted Steels Processed via Continuous Galvanizing Heat Treatments

Two galvanizable high-Al, low-Si transformation-induced plasticity (TRIP)–assisted steels were subjected to isothermal bainitic transformation (IBT) temperatures compatible with the continuous galvanizing (CGL) process and the kinetics of the retained austenite (RA) to martensite transformation during room temperature deformation studied as a function of heat treatment parameters. It was determined that there was a direct relationship between the rate of strain-induced transformation and optimal mechanical properties, with more gradual transformation rates being favored. The RA to martensite transformation kinetics were successfully modeled using two methodologies: (1) the strain-based model of Olsen and Cohen and (2) a simple relationship with the normalized flow stress, \( \left( {{\frac{{\sigma_{\text{flow}} - \sigma_{YS} }}{{\sigma_{YS} }}}} \right) \). For the strain-based model, it was determined that the model parameters were a strong function of strain and alloy thermal processing history and a weak function of alloy chemistry. It was verified that the strain-based model in the present work agrees well with those derived by previous workers using TRIP-assisted steels of similar composition. It was further determined that the RA to martensite transformation kinetics for all alloys and heat treatments could be described using a simple model vs the normalized flow stress, indicating that the RA to martensite transformation is stress-induced rather than strain-induced for temperatures above the \( M_{s}^{\sigma } \).

Toughness of syndiotactic polystyrene/epoxy polymer blends: microstructure and toughening mechanisms

Thermoplastic/epoxy blends were formed using an amine-cured epoxy polymer and a semi-crystalline thermoplastic: syndiotactic polystyrene (sPS). Complete phase-separation of the initially soluble sPS from the epoxy occurred via ‘reaction-induced phase-separation’ (RIPS) or via ‘crystallisation-induced phase-separation’ (CIPS), depending upon the thermal processing history employed. Dynamic mechanical thermal analysis showed that no sPS was retained dissolved in the epoxy polymer. For RIPS, at concentrations of sPS of up to 8 wt%, the sPS is present solely as spherical particles. However, macro phase-separation, giving a co-continuous microstructure, accompanied by local phase-inversion, dominates the RIPS blends containing more than 8 wt% sPS. In the CIPS blends, the sPS is present as spherulitic particles, and this microstructure does not change over the range of sPS concentrations employed, i.e. from 1 to 12 wt% sPS. The pure epoxy polymer was very brittle with a value of fracture energy, G Ic, of about 175 J/m 2. However, the addition of the sPS significantly increases the value of G Ic, though the toughness of the RIPS and CIPS blends differs markedly. For the RIPS blends, there is a steady increase in the toughness with increasing content of sPS and an apparent maximum value of G Ic of about 810 J/m 2 is obtained for 8–10 wt% sPS. On the other hand, the measured toughness of the CIPS blends increases relatively slowly with the concentration of sPS, and a maximum plateau value of only about 350 J/m 2 was measured in the range of 8–12 wt% sPS. The relationships between the microstructure of the RIPS and CIPS sPS/epoxy blends and the measured fracture energies are discussed. Further, from scanning electron microscopy studies of the fracture surfaces and optical microscopy of the damage zone around the crack tip, the nature of the micromechanisms responsible for the increases in toughness of the blends are identified. For the RIPS blends, (i) debonding of the sPS particles, followed by (ii) plastic void growth of the epoxy matrix are the major toughening micromechanisms. The increase in toughness due to such micromechanisms is successfully predicted theoretically using an analytical model. In the case of the CIPS blends, the increase in the value of G Ic results from (i) crack deflection and (ii) microcracking and crack bifurcation.

Comparison and improvement of the high rate performance of different types of LiMnO spinels

Abstract The rate capacity especially the high rate discharge performance is another important aspect for the application of Mn-based spinel cathodes for EV/HEV power sources besides the cycling performance that is now intensively investigated. In this paper, spinel materials differing in chemical composition and thermal processing history were investigated by discharging at constant current rates from C/10 to 4 C at ambient temperature. It was found that the high-rate discharge capability of Mn-based spinels is very excellent if prepared at temperatures below 850 °C, no matter cation doping or not. In contrast, spinels synthesized over 950 °C showed much poorer high rate performance, and some kinds of impurities were proposed to be responsible for the deteriorated behavior. Annealing at lower temperatures was found to be useful for the significant improvement of the high rate discharge capability of Mn spinels.

A neutron reflectometry study of the interface between poly(9,9-dioctylfluorene) and poly(methyl methacrylate)

Neutron reflectivity was used to study the interface between the semiconducting polymer poly(9,9-dioctylfluorene) (PFO) and the insulating polymer poly(methyl methacrylate) (PMMA). The PFO/PMMA interfacial width was measured in the nematic and crystalline phases of the PFO, both with the PMMA on top of the PFO and vice versa. These interfaces are broad compared to atomic length scales, with measured interfacial widths in the range from 10 to 20 Å. We found that the interfacial width was independent of both the chosen geometry and the thermal processing history. The equilibrium interfacial width only depended on temperature, with the width in the nematic phase of the PFO being broader than in the crystalline regime.

Influence of SiC whisker on planar slip in Al-Li based alloys

The tensile deformation microstructure characteristics of silicon carbide whisker (SiCw) reinforced Al-Li and Al-Li-Cu-Mg-Zr composites prepared by squeeze casting technique were studied by means of transmission electron microscopy (TEM), in order to evaluate the influence of SiC whisker on planar slip in Al-Li based alloys. For the purpose of comparison, the microstructural features of the unreinforced matrix alloys with the identical fabrication, thermal processing and tensile deformation history were also investigated. Dislocation pairs and intense slip bands originated from cutting of δ′ (Al3Li) phases by moving dislocations, could be found in the specimens of Al-Li and Al-Li-Cu-Mg-Zr alloys, whereas absent in either SiCw/Al-Li or SiCw/Al-Li-Cu-Mg-Zr composites. The results demonstrate that the addition of SiC whisker to Al-Li based alloys, has a considerable effect on suppressing planar slip which is a general phenomenon in Al-Li based alloys resulting from the interaction between δ′ phase and dislocations.

Effects of thermal processing on thermal expansion coefficient of a 50 vol.% SiCp/Al composite

Abstract The thermal expansion coefficients (CTE) of a 50 vol.% SiCp/Al composite prepared by a squeeze casting route were measured and examined from room temperature to 600°C using thermomechanical analysis (TMA) method, under the conditions of as-cast (AS), water-quenched (WQ), furnace-cooled (FC) and air-cooled (AC). The influence of thermal processing on CTE of the SiCp/Al composite was studied in terms of thermal residual stresses generated upon cooling from the processing temperature. It is found that the introduction of high volume fraction of SiC particles to Al matrix could notably reduce the CTE of matrix, leading to the low CTE values of the composite either at room temperature or at high temperature. The CTEs of both the composite and the unreinforced Al matrix increase with increasing of temperature, while the composite shows a much slower increasing rate than the unreinforced Al matrix resulting from the restriction of SiC particles on Al matrix during thermal expanding process. The thermal expansion behavior of the SiCp/Al composite is influenced by the previous thermal processing history. The WQ and AS specimens present lower CTEs compared to the FC and AC ones, which is thought to be due to the difference in original thermal residual stresses within these specimens and their releasing behavior during subsequent heating.

Processing of Thick Dielectric Films for Power MEMS: Stress and Fracture

ABSTRACTThis paper presents residual stress characterization and fracture analysis of thick silane based PECVD oxide films. The motivation for this work is to elucidate the factors contributing to residual stress, deformation and fracture of oxide films so as to refine the fabrication process for power MEMS. It is shown that residual stress in oxide films strongly depended on thermal processing history. Dissolved gases were found to play an important role in governing intrinsic stress. The tendency to form cracks is a strong function of film thickness and annealing temperature. Mixed mode fracture mechanics was applied to predict critical cracking temperature, and there is a fairly good match between theoretical predictions and experimental observations.