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When processing low-quality gibbsite–kaolinite bauxites, technologies that involve different methods of mechanical and chemical enrichment with the separation of a difficult-to-utilize fine kaolinite fraction for disposal are used. Before production, problems related to waste storage and disposal arise. To solve the problem of utilization, it is necessary to develop an effective technology for the selective processing of the kaolinite fraction. The efficiency of the technology will depend on the quality of pretreatment of raw materials prior to processing for Al2O3 extraction. Preliminary preparation of kaolinite fraction is associated with the maximum removal of excess silica during chemical enrichment by treatment with an alkaline solution. The presence of silica reduces the quality of final alumina products and requires a large consumption of reagents during the desiliconization of aluminate solutions. During the chemical enrichment of kaolinite fraction in alkaline solution, a serious problem of the co-dissolution of Al2O3 with silica arises. The solution to this problem can be the transformation of phase composition with the transformation of kaolin into a chemically resistant compound corundum, which will create conditions for the selective removal of silica. Kazakhstan's alumina refinery, Pavlodar Aluminum Smelter, processes low-quality gibbsite–kaolinite bauxite from the Krasnogorsk deposit. To improve the quality of bauxite, preliminary gravity enrichment is carried out to separate the kaolinite fraction to a quantity greater than 50%. The purpose of this work was to study the possibility of the selective processing of the kaolinite fraction via various techniques, including preliminary thermal transformation, through sintering, chemical enrichment, autoclave leaching in a circulating aluminate solution, and low-temperature desiliconization, to obtain a solution for decomposition. As a result of this study, the possibility of obtaining a corundum phase after sintering at a temperature of 900–1000 °C was established, which made it possible to obtain 58.8% chemical enrichment through the extraction of SiO2 into solution. Further use of the enriched kaolinite fraction in autoclave leaching in a circulating aluminate solution with low-temperature desiliconization made it possible to obtain an aluminate solution with a caustic modulus of 1.65–1.7, which is suitable for decomposition. [ABSTRACT FROM AUTHOR]

Medieval wall paintings in the church of the monastery of St. John in Müstair (Switzerland) have been exposed to several fires over the last centuries. Non-invasive (hand-held-XRF) and microinvasive (PLM, SEM-EDX, XRPD, µ-Raman, and SERS) techniques were used to analyse 14 painted fragments from the Romanesque (c. 1200 CE) painting cycle recovered from the attic of the church above younger Gothic vaulting in order to study the microstratigraphy of the painted surfaces and determine alterations and newly formed products, with the aim of understanding if the darkening was directly attributable to contact with fire. Scientific, historical, and bibliographical research have shown that alteration processes in the pigments from these paintings are not directly linked with fires, except possibly for two lead-based painted fragments. This indicates that the action of the historically documented fires in the church was not uniform and did not affect all areas of the paintings equally. [ABSTRACT FROM AUTHOR]

Silica hydrogel derived from serpentine minerals was first used for the preparation of intermediate systems from the mixture composed of different SiO2/ZnO molar ratios via adapting a simple precipitation method previously developed. The effects of both stirring time and sintering temperature variation on the evolution and morphology of zinc silicate phases in those systems were examined by thermal analysis, X-ray diffraction study, scanning electron microscopy, energy-dispersive spectroscopy and Fourier transform infrared spectroscopy. Whatever the initial parameters are, well-crystallized α-Zn2SiO4 transformed from β-Zn2SiO4 exists at 900 °C. In the systems with the stoichiometric proportion of the initial reagents, the transformation of β-Zn2SiO4 into α-Zn2SiO4 starts at about 700 °C. In the ones wherein the content of SiO2 is a little greater (SiO2/ZnO 2:2) than that required, the stirring time extended up to 120 min decreases the temperature of α-Zn2SiO4 crystallization up to such lower values as 600 °C. The subsequent increase of SiO2 portion (SiO2/ZnO 3:2 and 4:2) promotes both the formation of β-Zn2SiO4 single phase distinguished by thermal stability up to 800 °C including and a product composed of α-Zn2SiO4 and cristobalite above 800 °C. α-Zn2SiO4 crystallites sizes variable from 57 up to 92 nm can be manipulated by stirring time. The increase of SiO2 excess substantially reduces the size of β-Zn2SiO4 particles from 60 up to 10 nm. [ABSTRACT FROM AUTHOR]

The preparation of supported high-density metal nanoparticles (NPs) is of great importance to boost the performance in heterogeneous catalysis. Thermal transformation of metal-organic frameworks (MOFs) has been demonstrated as a promising route for the synthesis of supported metal NPs with high metal loadings, but it is challenge to achieve uniform metal dispersion. Here we report a strategy of "spatial isolation and dopant anchoring" to resist metal aggregation in the pyrolysis of MOFs through converting a bulk MOF into dual-heteroatom-containing flower-like MOF sheets (B/N-MOF-S). This approach can spatially isolate metal ions and increase the number of anchoring sites, thus efficiently building physical and/or chemical barriers to cooperatively prevent metal NPs from aggregation in the high-temperature transformation process. After thermolysis at 1,000 °C, the B/N-MOFS affords B,N co-doped carbon-supported Co NPs (Co/BNC) with uniform dispersion and a high Co loading of 37.3 wt.%, while untreated bulk MOFs yield much larger sizes and uneven distribution of Co NPs. The as-obtained Co/BNC exhibits excellent electrocatalytic activities in both hydrogen evolution and hydrazine oxidation reactions, and only a voltage of 0.617 V at a high current density of 100 mA·cm−2 is required when applied to a two-electrode overall hydrazine splitting electrolyzer. [ABSTRACT FROM AUTHOR]

Carbon-based materials have become an indispensable component in a myriad of domestic and industrial applications. Most of the carbon-based end-of-life products discussed in this review end up in landfills. Where recycling is available, it usually involves the production of lower-value products. The allotropic nature of carbon has been analysed to identify novel materials that could be obtained from used products, which also transform into a secondary carbon resource. Thermal transformation of carbon-rich wastes is a promising and viable pathway for adding value to waste that would otherwise go to landfills. The valorisation routes of four different carbon-rich wastes by thermal transformation are reviewed in the study—automotive shredder residue (ASR), textile wastes, leather wastes, and spent coffee grounds (SCGs). Textile wastes were thermally transformed into carbon fibres and activated carbon, while ASRs were used as a reductant to produce silicon carbide (SiC) from waste glass. The leather wastes and spent coffee grounds (SCGs) were employed as reductants in the reduction of hematite. This paper examines the possible routes of thermally transforming carbon-rich wastes into different industrial processes and applications. The transformation products were characterised using several techniques to assess their suitability for their respective applications. The strategy of valorising the wastes by thermal transformation has successfully prevented those wastes from ending up in landfills. [ABSTRACT FROM AUTHOR]

Anorthite ceramics was fabricated from calcium exchanged Na-LTA zeolite. The powder compacts of Ca-LTA zeolite were sintered at different temperatures ranging between 1100 and 1400°C. It was found that the temperature of 1100°C was sufficiently high to trigger formation of anorthite which stayed stable even at temperature as high as 1400°C. The highest relative density and the lowest open porosity were measured in samples sintered at 1200°C for 3 h. The effect of milling time of Ca-LTA zeolite precursor on density, microstructure and mechanical properties of samples sintered at 1200°C for 3 h was investigated. The particle size refinement appeared to be beneficial in accelerating densification process and improving mechanical properties. The density, compressive strength and hardness of anorthite ceramics obtained from non-milled precursor were measured to be 70.5 %TD, 64 MPa and 1.45 GPa, respectively. On the other side the anorthite ceramics obtained from 24-hour-long milled zeolite precursor had density of 83.9 %TD, compressive strength of 101 MPa and hardness of 3.44 GPa.

Oxytetracycline (OTC) is an antibiotic authorized for use in aquaculture; it is often detected in seafood products, especially shrimp. Previous studies investigating the fate of OTC in shrimp tissues after cooking were limited to quantification of parent compound residues and did not describe any potential transformation products formed. Hence, the main objective of this study was to apply a nontarget analysis workflow to study the fate of OTC in shrimp muscle. Furthermore, “water” and “spiked” models were evaluated for their suitability to track the transformation of OTC in incurred muscle and to determine whether the matrix plays a role in the transformation pathway. First, four different extraction methods were compared for the determination of OTC in muscle. Second, raw and cooked samples were then extracted using a suitable method (acidified water–methanol–acetonitrile, with cleanup of samples achieved using freezing) and were analyzed by high-performance liquid chromatography quadrupole time-of-flight mass spectrometry. OTC levels were reduced by 75 and 87% in muscle and water, respectively. Identification of thermal transformation products was limited to formula generation, but results showed that different compounds were identified in spiked and incurred muscle. [ABSTRACT FROM AUTHOR]

Since the prehistoric era, hematite has been known as a reddish color pigment on rock art, body paint, and decorating substances for objects discovered almost worldwide. Recently, studies about purple hematite used in prehistoric pigment have been done vigorously to investigate the origin of the purple pigment itself. These previous studies indicate that the differentiation of crystallinity, crystal size, morphology, and electronic structure can cause the color shift, resulting in purple hematite. In this study, we conducted a detailed study of the sintering temperature effects on the formation of hematite minerals. This study aims to reveal the structural, crystallography, and electronic transformation in hematite due to heating treatment at various temperatures. The hematite was synthesized using precipitation to imitate the primary method of hematite formation in nature. The sintering process was carried out with temperature variations from 600 °C to 1100 °C and then characterized by crystallographic and structural properties (XRD, Raman Spectroscopy, FTIR), particle size (TEM), as well as electronic properties (DRS, XANES). The crystallinity and particle size of hematite tend to increase along with higher sintering temperatures. Moreover, we noted that the octahedral distortion underwent an intensification with the increase in sintering temperature, which affected the electronic structure of hematite. Specifically, the 1s → 3d transition exhibited lower energy for hematite produced at a higher temperature. This induced a shift in the absorbed energy of the polychromatic light that led to a color shift within hematite, from red to purple. Our finding emphasizes the importance of electronic structure in explaining hematite pigment’s color change rather than relying on simple reasons, such as particle size and crystallinity. In addition, this might strengthen the hypothesis that the prehistoric human created a purple hematite pigment through heating.

[Display omitted] • The optimized combustion conditions can utilize the heating value in coal and transform REY to easily leachable forms. • REY greatly enriched in ash below 45 μm, caused by the small mineral grain size and extensive mineral fragmentation in boiler. • The enhanced acid leachability was related to thermal decomposition of flurocarbonates, aluminophosphates, and organic-bound REY in coal. • Different speciation transformation behavior of REY during combustion resulted in distinct REY leaching behavior for different ash types. The extraction of rare earth elements (REE) from coal ash has attracted significant attention, but satisfactory solutions have not yet been achieved. Indeed, the REE extractability is largely determined by the transformation behavior of REE during coal combustion. This study found that the controlled combustion conditions of circulated fluidized-bed boiler (CFB) can both utilize the heating value and enhance the recovery of REE from coal. Tests were conducted using a bituminous coal with REE concentration of approximately 149 ppm in an industrial 35 t/h CFB boiler with controlled boiler loads and coal sources. Advanced automated image analysis by scanning electron microscopy (AIA-SEM) and sequential leaching procedure were employed to clarify the speciation transformation behavior of REE in boilers and investigate the effects of these transformations on the leachability of REE. Approximately 75 % of REE partitioned into fly ash and enriched in particles < 45 μm (∼710 ppm) after combustion. Acid leaching tests under mild conditions (1 M HCl at 60 ℃ and S/L = 1:25) performed on coal, bulk ashes, and sieved ashes revealed an improvement in REE leaching ratio from coal (21.34 %) to fly ash (71.07 %). Particle size played a crucial role in acid extractability, particularly for middle and heavy REE in cyclone ash but had no influence on those in fly ash. The dominant forms of REE in coal including Ca-REE fluorocarbonates (36.7 %), aluminophosphates (12.0 %), and organic-bound REE (approximately 20 %) significantly decreased, contributing to the formation of leachable rare earth oxides (∼65 %) in ash. Furthermore, the small size of REE mineral grains in coal (over 50 % below 5 μm) and extensive mineral fragmentation occurring in boiler resulted in the enrichment and enhanced REY leachability in fine ash. [ABSTRACT FROM AUTHOR]

Schwertmannite is a metastable mineral playing a crucial role in the immobilization of metal(oid)s in acid mine drainage (AMD) systems. High temperatures associated with wildfires could lead to a sudden schwertmannite transformation, changing the mobility of metal(oid)s. The objective of the present study was to examine the thermal transformation from schwertmannite to hematite, and the subsequent effect on the chromium partitioning. The immobilization of arsenate after thermal transformation and its implications on chromium mobility was also evaluated. Natural schwertmannite, with increasing contents of chromium, was thermally treated between 200 to 800 °C. Transformation products were characterized by solid-phase techniques and selective chemical extractions. Results indicated a transformation to hematite at temperatures above 400 °C. The presence of chromium barely affected the temperature at which the transformation occurred, although partitioning of chromium in the mineral changed with temperature. As the temperature increased from 25 °C to 400 °C, chromium was less mobile and less outcompeted by arsenic adsorption, suggesting a larger contribution of inner-sphere complexes with increasing temperature. At temperatures above 600 °C, non-mobile forms strongly associated with neo-formed hematite were found. Finally, neo-formation of hematite led to a decrease in arsenic adsorption, implying a potentially enhanced arsenic mobility in AMD systems upon wildfires. [ABSTRACT FROM AUTHOR]

This paper presents results of a study of photochemical and thermal transformations of ammonium heptamolybdate-modified aluminosilicates. The optical density of UV irradiation-induced molybdenum polyoxometallate species increases with increasing porosity and interlayer spacing in the aluminosilicates in going from the zeolite to bentonite, and their chemical structure and properties are determined by the chemical composition of the ammonium heptamolybdate-containing mixtures and the surface chemistry of the solid matrices. The molybdenum polyoxometallates photoinduced in the structure of the aluminosilicates differ in spectral characteristics from irradiated ammonium heptamolybdate solutions containing the additives used, but offer considerably higher stability. In addition, preliminary UV irradiation of the zeolite containing ammonium heptamolybdate complexes occluded in its pores initiates a thermal transformation of polyoxometallate structures, resulting in the formation of Mo2O3 nanoclusters at 300°C and MoO3 nanoclusters at 700°C. UV irradiation of intercalated bentonite first leads to some expansion of interlayer spaces as a result of the formation of molybdenum polyoxometallate clusters, but subsequent heat treatment markedly densifies the structure, which is accompanied by the formation of molybdenum oxide particles in the temperature range 300–700°C and slight amorphization of the mineral. [ABSTRACT FROM AUTHOR]

Methylammonium paradodecatungstate, (CH3NH3)10[H2W12O42] ⋅ nH2O, was prepared by the reaction of WO3 or H2WO4 in aqueous methylamine, followed by drying. The [H2W12O42]10− anion consists of two HW3O13 groups containing three edge‐sharing WO6 octahedra and two W3O14 groups having two edge‐sharing connections. On drying the produced material at 70 °C, some lattice water was released, but this did not affect the [H2W12O42]10− structure, although there was a decrease in the unit cell volume. By adding water, the loss of lattice water and structural changes were reversed. The existence of paradodecatungstate anions was confirmed by single‐crystal and powder X‐ray diffraction, Fourier transform infrared, Raman, 183W nuclear magnetic resonance, and ultraviolet‐visible spectroscopy. When the methylammonium paradodecatungstate was heated to more than 150 °C, CH3NH2 and H2O were released, and amorphous WO3 was observed as an intermediate product and monoclinic WO3 as the final product. These results reveal the structure of methylammonium tungstate, which was first reported in 1909 and now is used as an important negative staining reagent for virus observation, is methylammonium paradodecatungstate. [ABSTRACT FROM AUTHOR]

Schwertmannite is sensitive to changes in geochemical, thermal, and microbial conditions. Changes in aqueous pH beyond its stability, i.e. pH 2.5–4.5, triggers its transformation to jarosite or goethite in highly acidic environments (pH ≤ 2.5), depending on the availability of jarosite-directing cations (Na+, NH4+, K+, etc.), while goethite is the common stable end product at pH > 7.5. Schwertmannite with degraded morphology can stably exist for years in oxic intermediate pH environments (pH 5.5–6.5), but the presence of trace amounts of Fe(II)aq yields goethite/lepidocrocite within a few hours, especially at pH ≥ 6.5. Hematite is the sole end product at ≥ 600 °C dry heating, with goethite and ferrihydrite as intermediate phases. Siderite, maghemite, and mackinawite form in anoxic microbial conditions due to dissimilatory reduction of Fe(III) and SO42− to Fe(II) and HS−, while orpiment forms from As(V)-rich schwertmannites. Sorbed contaminants enhance schwertmannite stability by restricting Fe(II)–Fe(III) electron transfer and microbial degradation by occupying surface sites. Although Fe(III) and sorbed ion mobilization typically has negligible effects on schwertmannite transformation, complete schwertmannite-SO4 release is likely in extreme conditions, and in microbial Fe(II)aq-rich media. Dissolution–reprecipitation and solid state transformation mechanisms broadly govern schwertmannite transformation. [ABSTRACT FROM AUTHOR]

Focused on uncoated ceramics, this tutorial paper is divided into two main sections. The first section deals with the operational phases required prior to firing (drying, piling, fuel supply). Then, the second chapter deals with the transformations that occur in the clayey paste during firing. An overall understanding of the firing process includes several issues to be considered and properly investigated. Thereafter, the thermal behaviour of several mineralogical phases (calcite and dolomite; quartz and cristobalite; K-feldspar and plagioclase; rutile and anatase; haematite, maghemite, hercynite and metallic Fe; illite, muscovite, biotite and chlorite; wollastonite, melilite, anorthite and monticellite; diopside and kaolinite) is described. Four brief chapters are further dedicated to the development of the amorphous/glassy component, to the matrix and its porosity, to the colour and the organic matter and to the variations in chemical composition, respectively. The concluding remarks provide a short list of the analytical techniques that have been commonly applied to the investigation of firing conditions and a concise summary of the state of the art of the “firing issue”. The method to be applied in future experimental reproductions and the opportunity itself to investigate the “firing issue” in various contexts are further discussed. [ABSTRACT FROM AUTHOR]

The thermolysis reactions of benzoazacyclodecatrienes under microwave irradiation conditions in toluene at 150 °C afforded complex azabenzo[ a ]cyclopropa[ cd ]azulene and (epiminomethano)cyclopenta[ a ]indene frameworks. Cyclopropanes were established as intermediates of the ultimate thermolysis products. [ABSTRACT FROM AUTHOR]

In this work, α-tricalcium phosphate (α-TCP) was successfully prepared by the thermal transformation of amorphous calcium phosphate (ACP) precursor. β-cyclodextrin (β-CD) was used for preparation of ACP precursor and played an important role in designing its special structure. The phase composition and microstructures of the obtained α-TCP at different annealing temperature were analysed by X-ray diffraction and scanning electron microscope, and confirmed that α-TCP can be prepared at 650°C for 3 h using ACP as precursor, which is much lower than the phase transition temperature of α-TCP. Mechanical properties were tested 24 h after mixing the obtained α-TCP with 30 wt.% of deionised water. The compressive strength and the flexural strength were 26.4MPa and 12.0MPa, respectively. The flexural strength was higher than that of α-TCP prepared by other methods.

Visible-light-driven stacked-layer heterogeneous photocatalyst carbonitride/tungstophosphate (TCN) was constructed via in-situ solid-state thermal transformation using melamine phosphotungstate (MPW). The structural, morphological and optical properties of the samples were investigated. Compared to the MPW hybrids and phosphotungstic acid hydrate, the TCN photocatalysts showed excellent visible light photocatalytic activity. During the thermal transformation, the melamine molecules polymerize to form the defective heptazine structure carbonitride attached to the surface of mixed-valence Keggin units. The interfacial POMs anions-π interactions, ligand-to-metal charge transfer and mix-valence organic-POMs structure makes the electrons fully delocalized over the MPW hybrids, and the TCN photocatalysts obtain the extended light absorption. The Keggin units accept and transfer electrons, so the recombination of photogenerated carriers is suppressed. 13TCN-390 obtains the optimal photocatalytic activity, its photocatalytic degradation efficiency of imidacloprid and rate constant k are 6.38 and 13.50 times than that of CN-390, respectively. The enhanced photocatalytic activity arises from the extended light absorption, suppressed photogenerated carriers' recombination, surface structure defect and suitable band structure. h+ and OH are the main reactive species when the proposed photocatalytic mechanism was done. This study provides a promising construction strategy for polymer/POMs photocatalysts using different organic-POMs hybrids. [ABSTRACT FROM AUTHOR]

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Abstract Three clinoptilolite-based materials, with Ba2+/NH 4 + ratios of 2.27, 0.60 and 0.11, were prepared starting from a powder containing about 90% of NH 4 -clinoptilolite. The samples were submitted to thermal treatments of 2 h up to 1200 °C. Further treatments were carried out at 1100 and 1200 °C for 4, 8, 16 and 32 h. The sequence of reactions observed in heating (NH 4 , Ba)-clinoptilolite is: dehydration; de-ammoniation (along with residual dehydration); dehydroxylation; amorphization; crystallization of new phases. Amorphization temperature varied from 700 to 900 °C, and increased with barium content. Monocelsian, mullite and cristobalite/tridymite were obtained from all samples heated 32 h at 1100 °C, along with residual glass that never exceeded 9%. The Ba2+/NH 4 + ratio resulted the main factor in determining type and quantity of the phases formed in the fired products, as well as their order of crystallization, but also temperature and duration of treatment affected the result. At 1100 °C mullite crystallized as last phase in the Ba-rich sample, and it did not form at 1200 °C. Similarly, celsian was never obtained at 1200 °C from the ammonium-rich material, and was the last phase to crystallize at 1100 °C. Transformations were faster at 1200 °C, but the amounts of residual glass were higher. Hexacelsian, the metastable polymorph of Ba-feldspar which is always formed during the heating of Ba-exchanged zeolites A and X, was never recorded among crystallization products obtained from (NH 4 , Ba)-clinoptilolite. Graphical abstract Image 1 Highlights • (NH 4 , Ba)-clinoptilolite (Ba2+/NH 4 +: 0.11; 0.60; 2.27) were heated up to 1200 °C. • Monocelsian + cristobalite/tridymite + mullite formed in samples heated at 1100 °C. • The lowest residual glass contents (<9%) were attained after 32 h at 1100 °C. • Hexacelsian did not form upon heating. [ABSTRACT FROM AUTHOR]

Abstract We reported a new layered ZnCo 1.5 (OH) 4.5 Cl 0.5 ·0.45H 2 O which crystallizes in two-dimensional (2D) nanosheets morphology in our previous work. Herein, two-dimensional hexagonal ZnCo 2 O 4 nanosheets were synthesized by the thermal transformation of the ZnCo 1.5 (OH) 4.5 Cl 0.5 ·0.45H 2 O precursor. Benefiting from this special hexagonal nanosheet morphology, the as-prepared ZnCo 2 O 4 electrode has induced a pseudo-capacitance contribution, leading to a stable discharge capacity of 688 mAh g−1 (at 5.0 A g−1) over 1000 cycles. To the best of our knowledge, the rate performance of ZnCo 2 O 4 for lithium ion batteries (LIBs) is superior to those of previously reported ZnCo 2 O 4 electrodes. Further applied to sodium ion batteries, ZnCo 2 O 4 electrode show fascinating performance with the specific capacity of 463 mAh g−1 after 60 cycles. This study provides a promising strategy for developing high-quality ZnCo 2 O 4 nanosheet electrodes for long-cycle-life and high-power LIBs and sodium ion batteries (SIBs). Graphical abstract Image 1 Highlights • Hexagonal ZnCo 2 O 4 nanosheet has been synthesized from the hydroxide precursor. • Our ZnCo 2 O 4 electrode exhibits high-rate performance for lithium ion battery. • Our ZnCo 2 O 4 electrode show fascinating performance in sodium ion storage. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Pulsed laser ablation of iron in air led to magnetite and iron nitrides formation. • Lamellas and rolls appear in the sample that was ablated in air, not in Ar-O 2 mixture. • Thermal treatment allowed control of the composition and structure of the material. • Materials obtained with different properties are in demand for different applications. Abstract Magnetic nanoparticles were obtained using the nanosecond pulsed laser ablation (Nd:YAG laser, 1064 nm, 7 ns) of an iron target in air at atmospheric pressure. The particles obtained were further annealed at four different temperatures. The composition, structure and properties of all obtained powders were investigated using X-ray diffraction (XRD), DSC, attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), Raman spectroscopy, TEM, SAED and other techniques. The initial sample was found to contain monoclinic magnetite and iron nitrides. Presumably, magnetite presents in the form of spherical particles with the distribution maximum of 12–15 nm, and nitrides take the form of lamellas and rolls. Thermal treatment of the sample led to particle enlargement and phase transformations, first, to cubic magnetite, then to a Fe 3 O 4 , α-Fe 2 O 3 and γ-Fe 2 O 3 mixture, and finally to the pure hematite phase. Zeta-potential, BET surface area and magnetic properties changed with the annealing as well. The obtained materials exhibited different properties that make them in demand in different fields, from biomedicine to technology. [ABSTRACT FROM AUTHOR]

Abstract This paper details the synthesis of copper-based products (i.e. Cu, Cu-Ni-Sn, Cu-Sn) from printed circuit boards (PCBs) using thermal transformation at 500 °C. The temperatures investigated in this paper are much lower than those used in conventional electronic waste smelting industries. This helps in reducing the energy requirements of the process opening up pathways for sustainable PCB processing technology. The resulting copper-based product comprises up to 94% metallic Cu, 2.5% Cu-Ni-Sn and 0.7% Cu-Sn alloys. Metallic Cu and Cu-Ni-Sn alloy are present in face centered cubic (FCC) form whereas Cu-Sn alloy possesses hexagonal closed packed (HCP) structure. XPS attests complete absence of oxides in metallic Cu. The copper product exhibits 4.57 × 107 ± 0.084 S m−1 electrical conductivity, equivalent to 78% IACS (International Annealed Copper Standard), which potentially enables its application in electrical switches or wire terminals. We have thus successfully developed a copper-based product from electronic waste, studied its properties and explored it from an application point of view. Graphical abstract Image Highlights • A copper-based product from PCBs obtained through thermal transformation at 500 °C. • Consists of metallic Cu, Cu-Ni-Sn and Cu-Sn alloy. • Metallic Cu and Cu-Ni-Sn alloy are in FCC form whereas Cu-Sn alloy is in HCP state. • Electrical conductivity corresponds to 78% IACS conductivity. [ABSTRACT FROM AUTHOR]

The disposal of clayey quarry sludges generated during aggregate washing process, represents significant environmental impacts and additional economic burden for the aggregate production industry. In this paper three different quarry sludges were sintered and investigated at the range 900-1100 °C using X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, and Fourier-transform infrared spectroscopy. Blends of the considered quarry sludges were studied and their physical properties (density, shrinkage, water absorption and compressive strength) were assessed. The effect of firing temperature on these properties was estimated and linked to the microstructure changes during heat treatment. The results revealed that anorthite, hematite, portlandite and lime were the neoformed phases. Breakdown products of clay minerals and carbonates contributed to the formation of some of these phases. The measured properties were strongly influenced by the firing temperature. Considering the measured technological properties, ceramic bodies with good mechanical performances (70 MPa) could be manufactured in the aforementioned conditions. [ABSTRACT FROM AUTHOR]

Plastics from electronic waste pose significant environmental and ecological threats due to several reasons, including, poor recyclability, complex nature, and significant increases in volumes of e-waste. In the present study, plastics from end-of-life printers were utilized as an alternative source of carbon in low-temperature reduction of iron oxide. As-received mixed plastic waste was characterized using several analytical tools and styrene acrylonitrile (SAN) was found to be the dominant plastic in the waste. Thermogravimetric analysis (TGA) was used to determine degradation kinetics of SAN plastics. SAN was subjected to thermal treatment in a horizontal tube furnace at 900 °C to evaluate the gaseous and solid products obtained and assess its suitability as a carbonaceous resource. In the present study, waste toner powder was utilized as a source of iron oxide. A heated platen press was employed to pelletize raw SAN and waste toner powder, which were then subjected to thermal transformation at 900 and 1100 °C. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses on the reduced samples indicate the partial reduction of iron oxide to metallic iron. This suggests that the SAN plastics from end-of-life printers can potentially be used as a partial replacement for conventional and non-renewable carbonaceous materials in iron oxide reduction, enabling cleaner and sustainable production of iron. [ABSTRACT FROM AUTHOR]

The thermal transformation of Ba-exchanged zeolite A into the monoclinic polymorph of Ba feldspar celsian (BaAl 2 Si 2 O 8 , a ceramic material of great technological interest) was found to be affected by a number of different parameter, such as the temperature and duration time of the thermal treatment, the forming pressure, the presence of the mineralizing cation Na + and Li + , and Sr 2+ doping. These facts were investigated in a long term study which is critically reviewed in this work, thus supplying the reader with an overall vision of this complex matter. Moreover, it is evidenced that the thermal transformation of Ba-exchanged zeolite A appears the most profitable and simple way to obtain the synthesis of the monoclinic polymorph of Ba feldspar celsian, which can be attained in few hours thermal treatments at 1000–1100 °C. The mechanisms on which these transformations are based and the sintering of monoclinic celsian powders obtained from Ba-exchanged zeolite A are discussed. [ABSTRACT FROM AUTHOR]

The thermal decomposition and de-hydroxylation process of dickite-potassium acetate (KAc) intercalated complex was studied using thermogravimetric (TG), differential thermal analysis (DTA), XRD and FTIR. The stability of intercalated complex was affected by heat treatment directly. The TG-DTA results showed that four changes had occurred at 64.5, 118, 301 and 406 °C, which can be attributed to (a) the loss of adsorbed water, (b) loss of the water linked to acetate ion in the layer of dickite, (c) decomposition of KAc, and (d) loss of water through de-hydroxylation, respectively. The XRD and FTIR results showed that when the heating temperature exceeded 400 °C, inner surface hydroxyls and inner hydroxyls lost gradually, generating amorphous meta-dickite. Further researches demonstrated that phase transition temperature of meta-dickite and mullite changed a lot through the intercalated KAc. [ABSTRACT FROM AUTHOR]

To evaluate the effect of pre-stress parameter on hardening-layer thickness during grinding process， surface grinding hardening process was applied to unquenched 45# steel workpiece at different pre-stress (0~100MPa) conditions. In a sequence of “thermal-force” loading order， grinding hardening process was simulated using the ANSYS software. Furthermore， how thermal transformation and work hardening influence layer thickness and thickness distribution at different location from grinding wheel's entry point were discussed. Thickness simulation data shows that the calculation error is less than 6%， indicating that the results are in good agreement with the experimental data. Meanwhile， the pre-stress loading leads to the slight reduction of thickness (<10%) on the surface grinding hardening-layer， which proves that loading pre-stress provokes re-distribution of microstructure， suppresses diffusion of quenched carbide， but probably is not a beneficial factor to increase hardening layer thickness. [ABSTRACT FROM AUTHOR]