Increase Of Thermal Treatment Temperature Research Articles

Structural properties and failure characteristics of granite after thermal treatment and water cooling

In a variety of fields such as exploitation of geothermal energy and the reconstruction of nuclear waste storage, both of high-temperature and cooling process change the physical and mechanical properties of granite. Uniaxial compression tests were performed on five groups of granite samples at 25 °C, 200 °C, 400 °C, 600 °C and 800 °C after water cooling, and CT scanning, acoustic emission(AE) monitoring and X-ray diffraction(XRD) scanning were used to investigate the structure properties and failure characteristics of granite. It is found that the proportions of pore volume greater than 106 μm3 and less than 105 μm3 with are positively and negatively correlated with the thermal treatment temperature respectively. The mechanical properties of granite are significantly deteriorated by temperature gradient shock, and crack development scale during failure process overall increases as implied by AE response. The failure intensity index η is proposed to characterize the failure severity of granite, and the value of η descends with the increase of thermal treatment temperature, indicating the failure severity of granite is alleviated. Three types of loading failure mode are classified for water-cooled high-temperature granite. The failure mode of granite at 200 °C and 600 °C is tensile failure and tensile-shear failure respectively, while the granite samples are dominated by shear failure at 25 °C, 400 °C and 800 °C.

Integrated utilization of coal gangue for synthesis of β-Sialon multiphase ceramic materials

To realize the effective utilization of the industrial waste coal gangue, in this study, β-SiAlON multiphase ceramic material was successfully prepared using coal gangue as main raw material. The thermodynamic analysis of β-SiAlON synthesis was firstly performed. We also investigated the performance of the synthetic materials under different conditions. We found that an increase in thermal treatment temperature promotes the formation of the β-SiAlON phase. The optimal holding time was determined to be 4 h at 1500 °C, under which the flexural and compressive strengths of the material were 10.1 MPa and 24.7 MPa, respectively. Meanwhile, the shrinkage and porosity value were 13.1% and 22.3%, respectively. At last, the reaction direction of impurity elements and the migration of heavy metals in the synthesis process were also mentioned.

Changes of phosphorus species during (hydro) thermal treatments of iron-rich sludge and their solubilization mediated by a phosphate solubilizing microorganism

This study systematically evaluated phosphorus (P) solubilization from pyrochar and hydrochar derived from both raw sludge and iron-rich sludge. The data indicated, that an increase in thermal treatment temperature and the presence of iron promoted the accumulation of P in both pyrochar (derived at 300, 500, and 800 °C) and hydrochar (derived at 100, 200, and 280 °C). After incubating pyrochar and hydrochar with a phosphate solubilizing microorganism (PSM) (Pseudomonas aeruginosa) for 30 days, PSM significantly promoted the solubilization of P in pyrochar and hydrochar synthesized at low temperatures rather than those at high temperatures, with a 59 % increase for the pyrolysis of raw sludge at 300 °C than that pyrolyzed at 800 °C and a 62 % increase for the hydrothermal treatment of raw sludge at 100 °C than that treated at 280 °C. And the phenomena were more obvious on the char samples derived from iron-rich sludge. The mass balance of different P species in the solid and liquid phases indicated that after incubating with PSM for 30 days, NaOH-P was the main P solubilized from the solid phase of pyrochar and HCl-P was the main P solubilized from the solid phase of hydrochar. Considering P availability to plants, the preliminary economic analysis indicated that the hydrothermal treatment of iron-rich sludge at 100 °C showed the highest economic benefits for P recovery, with the net cost of 28.79 USD/ton wet sludge. This study was useful in giving novel insights into the reuse of char samples as P fertilizer, and also suggested the importance of Pseudomonas aeruginosa and other bacteria in sludge application, particularly in terms of P solubilization.

Effect of different thermal treatment temperatures on dimensional stability and mechanical properties of M50 steel

By using field-emission scanning electron microscopy, X-ray diffraction, impact and tensile-property tests, the effect of thermal treatment temperatures in stabilization treatment on the microstructure, dimensional stability and mechanical properties of M50 bearing steel was studied. Results show that the size of M50 steel decreases due to carbide precipitation at 400 °C, 420 °C, 440 °C and 480 °C, and increases due to martensite transformation at 460 °C. In the thermal treatment temperature range of 400–480 °C, the amount of secondary carbide precipitation in M50 steel increases first and then decreases with the increase of thermal treatment temperature, and the amount of carbide precipitation in the steel reaches the maximum at 460 °C. During the thermal treatment temperature range of 400–460 °C, the residual austenite gradually decomposes and decreases in quantity. However, at 480 °C, the residual austenite has relatively higher carbon content to make it more stable and less likely to decompose. At the same time, the tensile properties are slightly improved, the impact toughness decreases at 460 °C and improved under other conditions.

Effect of TBC of raw milk and thermal treatment intensity on endotoxin contents of milk products

Endotoxin in dairy products may pose risks to consumers’ health, but the effects of raw-milk total bacterial count (TBC) and thermal treatment temperature on endotoxin content of dairy products are not clear. In this study, TBC of raw milk and processed milk with different thermal treatment temperatures were detected by pilot processing experiment. We then verified it by detecting the endotoxin content of commercial dairy products. TBC was determined by conventional culture method, and the changes in alkaline phosphatase (ALP) and lactoperoxidase (LPO) activities in bovine milk before and after heat treatment were determined. The levels of fatty acids in bovine milk were detected by gas chromatography using a flame ionization detector (GC-FID). In the pilot experiment, raw milk was treated at 72, 75, 80, 85, 90, 95, 100, 105, 110, 115, and 120 °C for 15 s. After that, the raw milk was stored at 20 °C for 24 h and 48 h to greatly increase the TBC, and treated at 75 °C for 15 s and 90 °C for 15 s. The results show that the endotoxin content of sterilized milk increased with the increase in TBC and thermal treatment temperature. With the increase in thermal treatment temperature, the activities of ALP and LPO with endotoxin inhibition decreased. In addition, a total of 226 dairy samples were tested. The endotoxin content of 37 commercial PM milk samples were 6 EU/ml to 231 EU/ml, with 31 EU/ml to 1437 EU/ml for 40 commercial UHT milk samples, and 6 EU/ml to 9080 EU/ml for 149 reconstituted IFM samples. There was a significant difference in the endotoxin content of different dairy products (P < 0.05), and there was no significant difference between domestic and imported IFM (P > 0.05). This study found that TBC and thermal treatment temperature of raw milk could affect the endotoxin content of dairy products.

Multiscale investigation on molecular structure and mechanical properties of thermal‐treated rigid polyurethane foam under high temperature

AbstractIn order to study the relationship between the molecular structure and mechanical properties of rigid polyurethane foam (RPUF) during the mechanical and chemical failure process, the variation of the molecular structure and mechanical properties of RPUF treated in temperature range of 323–473 K were characterized by both theoretical and experimental methods. The molecular structure stability of RPUF varied with thermal treatment temperature was characterized by density functional theory method. The mechanical properties of base material of RPUF were simulated by means of molecular dynamics (MD) simulation. Then the related parameters obtained from the MD simulation were assigned into a representative volume element model of RPUF for the finite element analysis. The results indicated that the vibrational frequencies of isocyanate groups and amino acid ester groups in RPUF molecule increased while the molecular orbital energy gap of RPUF decreased with the increase of treatment temperature. It indicated that the RPUF molecule had high chemical reactivity at high temperature. The results of the multiscale simulation of mechanical properties showed that the defects and voids in RPUF generated under high temperature would grow with the increase of thermal treatment temperature, which intensified the stress concentration in RPUF and decreased the tensile properties of RPUF.

COMBINED EFFECT OF PYROMETALLURGICAL AND HYDROMETALLURGICAL PROCESSES ON QUARTZ ORE PURIFICATION

Recent advances in high-tech applications have highlighted the growing demand on highly pure silicates like quartz. Therefore, purification of quartz ore was determined as the subject of this study performed by pyrometallurgical followed by hydrometallurgical processes. In this research, the effect of thermal treatment (TT) followed by oxalic acid (OA) bleaching of quartz was examined to have a better understanding on the relationship between Fe remaining in concentrate and colour response. The level of TT temperature was found to have a significant effect on the purification of quartz by OA. The maximum Fe rejection rate was observed to occur both for non-treated and TT quartz up to 250°C. TT between 400°C and 900°C showed poor purification performance: decreasing L* value, and increasing a* and b* values. It is important to note that further increase in TT temperature to 1100°C resulted in the poorest bleaching: Fe rejection rate decreased, but colour response improved providing the highest L* value and the lowest a* and b* values. This finding was explained by the formation of dissolution resistant iron silicates. Moreover, the rate of Fe removal from quartz ore and differences observed in its colour response by OA bleaching were explained by changes in crystalline structure and formation of microcracks.

Size-driven phase transformation and microstructure evolution of ZrO2 nanocrystallites associated with thermal treatments

Thermal stability of nanocrystallites plays an important role in the manufacturing and application of nanocrystalline ceramics/glass-ceramics. This study explores the effects of thermal treatments on the microstructures of two ZrO2-SiO2 nanocrystalline glass-ceramics (NCGCs), an undoped one and a yttria-doped one. The two as-sintered NCGCs were composed of tetragonal (t) and monoclinic (m) ZrO2 nanocrystallites, and SiO2 component was amorphous. t-ZrO2 and m-ZrO2 nanocrystallites were metastable during thermal treatment. The content of m-ZrO2 in the undoped ZrO2-SiO2 NCGC first increased after thermal treating at 850 °C for 5 h, then decreased after thermal treating at and above 950 °C. After thermal treating at 1250 °C for 5 h, t-ZrO2 nanocrystallites experienced a rapid phase transformation during cooling, resulting the formation of 88.6 vol% m-ZrO2. Size-driven phase transformation was utilized to explain the metastability of t-ZrO2 and m-ZrO2 nanocrystallites. In contrast, the content of m-ZrO2 in the yttria-doped ZrO2-SiO2 NCGC continuously decreased with the increase of thermal treatment temperature. The addition of yttria improved the phase stability of t-ZrO2 up to at least 1250 °C. Crystallite size of both t-ZrO2 and m-ZrO2 nanocrystallites increased with the increase of thermal treatment temperature in the two NCGCs. The presence of residual thermal stress in the as-sintered NCGCs changed the lattice spacing of t-ZrO2 and m-ZrO2 nanocrystallites, and the stress can be released after thermal treatment. Thermal treatment exerts significant influences on the microstructure of ZrO2-SiO2 NCGCs.

Experimental Evaluation of Physical and Mechanical Properties of Geothermal Reservoir Rock after Different Cooling Treatments

A comprehensive understanding of the physico-mechanical behavior of rocks in hot dry rock (HDR) reservoir after different stimulation treatments is essential for the safe and effective exploitation of geothermal energy. In this study, the physico-mechanical properties of high-temperature granite (25–600 °C) subjected to slow cooling, water cooling, and liquid nitrogen (LN2) cooling were experimentally investigated, and the damage evolution and damage mechanism of the rock were discussed from the macro- and microscopic perspectives. According to the experimental results, the increase in thermal treatment temperature aggravates the deterioration of the physico-mechanical properties of granite specimens. It is found that 400 °C is the threshold temperature of the tested granite, after which the physico-mechanical properties of the rock present more prominent changes. Since LN2 can induce a more intense thermal shock within rocks, it has the most significant damage to the specimens compared with other two cooling methods, especially at a higher thermal treatment temperature. Acoustic emission (AE) monitoring can well reflect the failure process and the associated microcrack behavior of the specimens during loading. The results of thin slice analysis indicate that the generation and extension of microcracks are responsible for the macro-properties degradation of rocks. Both grain boundary and intra-grain microcracks are more common near quartz boundaries and inside quartz grains. The results in this study would shed light on performing HDR reservoir stimulations assisted with cryogenic LN2.

Preparation of highly porous Al2O3 aerogel by one‐step solvent‐exchange and ambient‐pressure drying

AbstractThis work presents the preparation of alumina aerogel via sol‐gel route utilizing ambient‐pressure drying. A novel and efficient solvent‐exchange process has been utilized as an alternative to conventional solvent‐exchange processes by directly boiling the hydro‐gel in solvent. High emphasis has been given in the selection of solvent based on polarity, boiling point, and specific gravity compared with water to facilitate efficient solvent‐exchange and reuse of the solvent. The ambient‐pressure‐dried alumina aerogel was thermally treated at temperature from 300°C‐1200°C to study the change in density, porosity, specific surface area, and microstructure along with crystalline properties. The ambient‐pressure‐dried alumina aerogel showed lower tapped density 0.108 g/cm3, specific surface area 519 m2/g, and total weight loss of 36.94% at 900°C. The degree of crystalline structure from amorphous was observed to increase with increase in thermal treatment temperature above 300°C, dominant above 700°C, whereas the transformation of bayerite γ‐Al(OH)3 to boehmite γ‐AlO2H was observed at 150°C‐300°C and to γ‐Al2O3 phase was observed at temperature of 300°C‐1200°C.

Synthesis and gas permeation properties of thermally rearranged poly(ether-benzoxazole)s with low rearrangement temperatures.

The diamine monomer, 9,9-bis[4-(4-amino-3-hydroxylphenoxy)phenyl] fluorene (bis-AHPPF) was successfully synthesized according to our modified method. A series of hydroxyl-containing poly(ether-imide)s (HPEIs) were prepared by polycondensation of the bis-AHPPF diamine with six kinds of dianhydrides, including 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), pyromellitic dianhydride (PMDA), 3,3′,4,4′-biphenyl tetracarboxylic diandhydride (BPDA), 3,3′,4,4′-oxydiphthalic anhydride (ODPA), 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and 4,4′-(hexafluoroisopropylidine)diphtalic anhydride (6FDA) followed by thermal imidization. The corresponding thermally rearranged (TR) membranes were obtained by solid state thermal treatment at high temperature under a nitrogen atmosphere. The chemical structure, and physical, thermal and mechanical properties of the HPEI precursors were characterized. The effects of heat treatment temperature and dianhydrides on the gas transport properties of the poly(ether-benzoxazole) (PEBO) membranes were also investigated. It was found that these HPEIs showed excellent thermal and mechanical properties. All the HPEI precursors underwent thermal conversion in a N2 atmosphere with low rearrangement temperatures. The gas permeabilities of the PEBO membranes increased with the increase of thermal treatment temperature. When HPEI–6FDA was treated at 450 °C for 1 h, the H2, CO2, O2 and N2 permeabilities of the membrane reached 239.6, 196.04, 46.41 and 9.25 Barrers coupled with a O2/N2 selectivity of 5.02 and a CO2/N2 selectivity of 21.19. In six TR-PEBOs, PEBO–6FDA exhibited the lowest rearrangement temperature and largest gas permeabilities. Therefore, thermally rearranged membranes from bis-AHPPF-based HPEIs are expected to be promising materials for gas separation.

Electromagnetic interference shielding properties of polymer derived SiC-Si3N4 composite ceramics

SiC-Si3N4 composite ceramics are successfully fabricated by pyrolysis of ferrocene-modified polycarbosilane (PCS) mixed with inert filler Si3N4 powders, followed by thermal treatment from 1100 °C to 1400 °C in Ar atmosphere. The porosity of SiC-Si3N4 ceramics decreases to 6.4% due to the addition of inert filler Si3N4. And the content and crystallization degree of free carbon and SiC derived from PCS are improved simultaneously with the increase of thermal treatment temperature. Finally, the free carbon and SiC interconnect, forming the conductive network. As a result, the electromagnetic interference (EMI) shielding performance of the as-prepared ceramic annealed at 1400 °C reaches up to 36 dB, meaning more than 99.9% of EM energy is shielded. The low porosity and high EMI shielding performance enable SiC-Si3N4 composite ceramics to be a promising electromagnetic shielding and structural material.

Preparation of indium tin oxide (ITO) thin film with (400) preferred orientation by sol–gel spin coating method

Tin doped indium oxide (ITO) thin films with (400) preferred orientation were fabricated by sol–gel spin coating method with metal indium and SnCl4·5H2O as indium and tin precursors, oxalic acid was used for synthesis of ITO sol as a stabilizer and methylcellulose as a binder. This study creatively combines thermal treatment at different temperatures with post-annealing treatment at 500 °C to prepare ITO thin films with enhanced conductivity and highly transmittance. It was found that the (400) preferred orientation growth strongly depends on thermal treatment temperature. Growth preferred orientation of the ITO thin films changed from (222) plane to (400) plane with the increase of thermal treatment temperature. The ITO thin film was thermal treated at 250 °C shows highly (400) preferred orientation, which exhibited an excellent conductivity (a low sheet resistance of 230 Ω Sq−1 and a low resistivity of 4.14 × 10−3 Ω cm) combining with a highly average transmittance of 85.12% and obtained the best figure of merit (8.68 × 10−4 Ω−1).

Effect of Thermal Treatment Temperature on the Flowability and Wax Deposition Characteristics of Changqing Waxy Crude Oil

The influence of thermal treatment temperature on the flowability and wax deposition characteristics of Changqing waxy crude oil was researched in detail through pour point/rheological tests, a cylindrical Couette wax deposition experimental device, DSC analyses, asphaltenes stability tests, and microscopic observations. It is found that the flowability of the crude oil can be greatly improved through increasing the thermal treatment temperature. Meanwhile, the wax deposition rate of the crude oil can be outstandingly inhibited with the increase of thermal treatment temperature from 50 to 70 °C. Moreover, the flow regime can also influence the wax deposition characteristics. Under cold flow regime (22 °C/12 °C), the structure of formed wax deposits is homogeneous while the aging of the wax deposits is not obvious. Under hot flow regime (30 °C/20 °C), the aging of the wax deposits is obvious, but a heterogeneous two-layer structure exists in the formed wax deposits at the thermal treatment temperatures 50 ...

Molecular Layer Deposition and Thermal Transformations of Titanium(Aluminum)-Vanadium Hybrid Organic-Inorganic Films

In this work Molecular layer deposition (MLD) technique used to synthesize titanium-vanadium (TiV x C y O z ) and aluminum-vanadium (AlV x C y O z ) hybrid organic-inorganic films via alternating surface reactions of titanium tetrachloride (or trimethylaluminum), vanadium oxochloride, and ethylene glycol. Using in situ monitoring it was found that the surface reactions were self-limiting at temperatures of 90 and 115°C. The coating thickness per molecular layer deposition cycle (growth rate) at 115°C on a silicon substrate varied from 5.8 to 11.4 A/cycle, and the film densities, from 1.7 to 2.0 g cm–3. An analysis of the samples obtained at 115°C revealed their amorphous structure. A thermal treatment of titanium-vanadium films at 450°C in air resulted in formation of highly structured coatings. These coatings were composed of nanowires of single-crystal vanadium oxide (V2O5) and mixed nanostructures of titanium and vanadium oxides. Increase in thermal treatment temperature to 500°C resulted in elongation of the V2O5 nanowires up to tens of micrometers and in their separation from the substrate. A thermal treatment of aluminum-vanadium films in air resulted in formation of a low-density film. Pyrolysis of the films in an inert gas yielded composite coatings containing domains of graphitized carbon. These films can be potentially useful in modern devices for energy storage, electronics, medicine and other promising fields of technology.

Improvement of vapor-phase silylation and thermal stability of silylated MCM-22 zeolite

The method of vapor-phase silylation over as-made MCM-22 was improved through the replacement of deionized water with NaOH solution that absorbed HCl produced during the vapor-phase silylation. Also, the thermal stability of silylated MCM-22 was investigated by X-ray diffraction, N2 adsorption–desorption, pyridine adsorption and desorption followed by infrared measurement and nuclear magnetic resonance techniques. The results showed that this improvement was beneficial for dichlorodimethylsilane molecules to enter the interlayer of MCM-22 zeolite to form pillaring structure. Both the interlayer pillaring structure and acidity of silylated MCM-22 varied with increasing thermal treatment temperature from 600 to 750 °C. Specifically, the interlayer pillaring Si groups were thermally stable below 650 °C, and damaged gradually with the increase of thermal treatment temperature from 650 to 750 °C, leading to gradual decrease of the specific surface area and volume corresponding to interlayer supercages. At 750 °C, the interlayer pillaring structure was destroyed completely, whereas the MWW structure was still maintained well. As to the variations of acid sites with thermal treatment temperature, different trend was observed. The amount of weak and strong Bronsted acid sites, as well as that of strong Lewis acid sites decreased gradually with increasing thermal treatment temperature to 650 °C, but remained almost unchanged when the temperature was further increased to 750 °C.

Natural gas purification and olefin/paraffin separation using cross-linkable 6FDA-Durene/DABA co-polyimides grafted with α, β, and γ-cyclodextrin

Using a cross-linkable co-polyimide (6FDA-Durene/DABA (9/1)), we have developed new flexible and high-performance gas separation membranes that can enhance both membrane permeability and plasticization resistance simultaneously by grafting various sizes of cyclodextrin to the polyimide matrix and then decomposing them at elevated temperatures. The gas permeability of thermally treated pristine polyimide (referred as the original PI) and CD grafted co-polyimide (referred as PI-g-CDs for 200 and 300 °C and partially pyrolyzed membranes (PPM)-CDs for 350, 400, and 425 °C) has been determined using O 2, N 2, CO 2, CH 4, C 3H 6, and C 3H 8 at 35 °C. The permeability of all gases increases with an increase in thermal treatment temperature from 200 to 425 °C. However, permeability increases more for those grafted with bigger size CD. Permeability of the original PI thermally treated at 425 °C is about 4–6 times higher than that treated at 200 °C. The permeability increase jumps to 8–10 times for PPM-α-CD and 15–17 times for PPM-γ-CD due to CD decomposition at high temperatures and bigger CD creating bigger micro-pores. Interestingly, the permeability ratios of PPM-α-CD to PPM-γ-CD and PPM-β-CD to PPM-γ-CD at 400 and 425 °C are around 0.6 and 0.8, respectively. These numbers are almost the same as the cavity diameter ratios of α-CD to γ-CD and β-CD to γ-CD. Clearly, the bigger CD creates the bigger micro-pores. Permselectivity decreases first with an increase in thermal treatment temperature up to 350 °C and then increases. Permselectivity of thermally treated CD grafted co-polyimide membranes is also slightly higher than that of the original PI due to higher degrees of cross-linking in CD grafted co-polyimide membranes. In addition, for co-polyimide membranes grafted by CDs, the higher thermal treatment temperature results in membranes with the better plasticization resistance to CO 2 and the better separation performance for 50:50 CO 2/CH 4 mixed gases. The best result for pure gas tests is achieved for PPM-γ-CD-425. This membrane has a CO 2 permeability of 4211 Barrers with a CO 2/CH 4 ideal selectivity of 22.44 and a C 3H 6 permeability of 521 Barrers with a C 3H 6/C 3H 8 ideal selectivity of 18.09. It can also resist against CO 2 plasticization until 30 atm. The CO 2 permeability drops slightly to 3976 Barrers with almost the same CO 2/CH 4 selectivity of 22.84 in mixed gas tests.

Effect of thermal treatment on adsorption–desorption of ammonia and sulfur dioxide on palygorskite: Change of surface acid–alkali properties

Thermally activated Palygorskite (Pg) has been found to be a good adsorbent material for ammonia (NH3) and sulfur dioxide (SO2). This research investigated the effect of thermal treatment on pore structure and surface acid–alkali properties of Pg through the adsorption–desorption of NH3 and SO2. The results showed that, up to 200°C, the adsorption of NH3 on Pg was significantly higher than SO2. This was due to NH3 being adsorbed in the internal surface of Pg and forming hydrogen bonds (H-bonds) with coordinated water. The increase in thermal treatment temperature from 150 to 550°C, showed a gradual decrease in the number of surface acid sites, while the number of surface alkaline sites increased from 200 to 400°C. The change of surface acidity–alkaline sites is due to the collapse of internal channels of Pg and desorption of different types of hydroxyls associated with the Pg structure.

Photocatalytic activity of titanium dioxide coatings: Influence of the firing temperature of the chemical gel

Heterogeneous photocatalysis can be exploited for the decomposition of micro-organisms which have developed on the surfaces of building materials. In this work, the efficiency of titanium dioxide coatings on fired clay products is examined. The sol–gel method is used to synthesize a fine TiO 2 powder with a specific surface area of 180 m 2 g −1. Thermal treatment of the chemical gel at 340 °C leads to crystallisation in the anatase phase and with further temperature increase, crystallite growth. For thermal treatments in the range 580–800 °C, there is a progressive transition from anatase to rutile. However, despite a decrease in specific surface area of the powder attributed to aggregation/agglomeration, the coherent domain size deduced from X-ray diffraction measurements remains almost constant at 23 nm. Once the transition is completed, increase of thermal treatment temperature above 800 °C leads to further crystallite growth in the rutile phase. The thermally treated titania powders were then sprayed onto fired clay substrates and the photocatalytic activity was assessed by the aptitude of the coating to degrade methylene blue when exposed to ultraviolet light. These tests revealed that the crystallite size is the important controlling factor for photocatalytic activity rather than the powder specific surface area or the anatase/rutile polymorph ratio.

PREPARATION AND PROPERTIES OF SUPERHYDROPHOBIC POLYPHENYLENE SULFIDE COMPOSITE COATINGS

A simple spray approach to fabricate superhydrophobic coatings on tile and glass substrates is presented. Commercial available polyphenylene sulfide (PPS) and hydrophobic silica (H—SiO2) powder were suspended in ethanol and the mixed suspensions were spray on substrates. After dried at different temperatures, surface coatings with different hydrophobicity were obtained. By observing the surface morphologies with scanning electron microscope ( SEM ) and atomic force microscope ( AFM ),and measuring water contact angles with a contact angle system,factors affecting the morphology,roughness and contact angle of the surface coatings,such as thermal treatment temperature and the weight ratio of H—SiO2 to PPS,were investigated in detail. With the increase of the thermal treatment temperature,both the surface roughness and the contact angle increased when the temperature was lower than 280℃ . As the weight ratio of H—SiO2 to PPS rose from 1∶ 10 to 1∶ 1,more H—SiO2 powders accumulated on the surface,leading to a significant increase of hydrophobicity. The surface coating obtained at 280℃ with the weight ratio of H—SiO2 to PPS 1 ∶ 1 showed a water contact angle higher than 150° and a sliding angle lower than 4°,exhibiting fascinating superhydrophobic properties. The surface coating could remain superhydrophobicity upon a further increase in thermal treatment temperature or the amount of H—SiO2 powder. Moreover,the surface coatings showed high contact angles,larger than 150°, for all the solutions with pH ranging from 1 to 14. The abrasion resistant property of the as-prepared superhydrophobic surface coating was tested using a homemade setup. Being scraped by freely-falling sands,the superhydrophobic coating could keep its high hydrophobicity,while a commercial hydrophobic coating transformed from hydrophobicity to hydrophilicity. This result implied our superhydrophobic surface coating was very stable. Moreover,chalk powders on the superhydrophobic surface coatings could easily be washed off with water,indicating good self-cleaning properties. The presented approach is convenient and can be potentially applied in fabrication of superhydrophobic surfaces in large scale.