镁合金微弧氧化着色膜研究

镁合金在电子工业中的快速发展对装饰性能提出了更高的要求.主要研究了如何在微弧氧化的同时进行氧化着色.膜层制备选取的基材为AZ91,电解溶液由硅酸盐为主的碱性溶液组成,配方为:Na2SiO3 5～30g/L,KMnO4 1～20g/L,NaOH 1～5g/L,KF 5～8g/L,Na3 C6H5O70.5～2g/L,EDTA 0.5～2g/L.在电解液中添加着色盐KMnO4,形成了颜色各异的黄色陶瓷膜层.研究发现,膜层呈现出黄色主要是由于在膜层中生成了Mg6MnO8相,该物相在氧化膜中含量不同和分布差异将导致样品颜色深浅不同.     

A novel hydrophobic adsorbent of electrospun SiO<Subscript>2</Subscript>@MUF/PAN nanofibrous membrane and its adsorption behaviour for oil and organic solvents

With increasing oil spill accidents, the development of effective and low-cost adsorbents with good hydrophobicity is highly desirable. To cope with the clean-up of oil spill, a hydrophobic adsorbent was synthesized by electrospinning using inexpensive raw materials. By ingeniously combining melamine with polyacrylonitrile (PAN) as well as SiO₂ nanoparticles, a novel composite nanoadsorbent named SiO₂@MUF/PAN nanofibrous membrane was prepared and characterized. The adsorbents were conducted based on uniform nanofibre networks and were abundant with narrow slit-like pores, which are significant for the retention of oil and organic solvents. The hydrophobicity of the as-prepared membranes was enhanced with an increasing amount of SiO₂, and the highest water contact angle was 128.3°. Furthermore, the combination of SiO₂ and melamine increased the thermal stability of the membranes. With the unique pore structures and hydrophobicity, the membranes were able to selectively remove not only oil but also organic solvents from water surface. The adsorption capacities of the membranes with SiO₂ nanoparticles (0.9 wt%) were the highest and that for peanut oil, diesel, pump oil and engine oil were 19.09, 13.12, 18.48 and 22.67 g g^?1, respectively, while that for organic solvents ranged from 12.92 to 22.16 g g^?1. After 10 adsorption–regeneration cycles, the adsorption capacity was still around 35% of the initial value. Due to its high oil adsorption capacity, excellent reusability and the cost-effective hydrophobic, SiO₂@MUF/PAN have a great potential for oil spill clean-up.     

Sm3+-doped La2O3–Al2O3–SiO2-glasses: structure, fluorescence and thermal expansion

This paper reports on the effect of the chemical composition on the glass structure, the coefficients of thermal expansion and the fluorescence properties of Sm³⁺-doped La₂O₃–Al₂O₃–SiO₂-glasses. The silica concentration was varied between 50 and 70 mol% and the La₂O₃:Al₂O₃ ratio between 50:50 and 30:70. The glass formation and the densities are evaluated and FTIR reflectance spectra, coefficients of thermal expansion and fluorescence lifetimes are determined. It is shown that high SiO₂ concentrations and low La₂O₃:Al₂O₃ ratios result in relatively high fluorescence lifetime (2.19 ms, ⁴G_5/2) and low coefficients of thermal expansion (4.6 × 10^?6/K). The coefficients of thermal expansion and the fluorescence lifetimes show a linear dependency on the ratio LaO_3/2/(AlO_3/2 + SiO₂).     

SiO2/sulfonated poly ether ether ketone (SPEEK) composite nanofiber mat supported proton exchange membranes for fuel cells

A composite membrane of silica (SiO₂)/sulfonated poly (ether ether ketone) (SPEEK) nanofiber mat impregnated with Nafion was fabricated and evaluated for its potential use as a proton conductor for high temperature polymer electrolyte membrane fuel cells. The supporting SiO₂/SPEEK composite nanofibrous skeleton was prepared via electrospinning of a mixture of SPEEK solution and silica sol prepared from tetraethyl orthosilicate (TEOS). The control of hydrolysis and condensation of TEOS enabled to form entangled SiO₂ networks miscible to SPEEK solution. The prepared SiO₂/SPEEK nanofiber mat was impregnated with Nafion^® to completely fill the inter-fiber voids to prepare a dense membrane. The morphology of the nanofiber mat and the composite membrane were observed by scanning electron microscopy and the presence of SiO₂ and SPEEK in the prepared nanofibers was confirmed by FTIR spectroscopy. Proton conductivity and swelling of the membrane were measured. The H₂/O₂ single cell test using the composite membrane as a PEM was performed. At a high temperature and low humidity condition (120 °C and 40 % RH), the maximum power density was 170 mW/cm² for the Nafion-impregnated SiO₂/SPEEK (40/60 w/w) composite nanofiber membrane that was 2.4 times higher than recast Nafion (71 mW/cm²) while SPEEK film failed.     

Effect of microwave heating on the microstructures and kinetics of carbothermal reduction of pyrolusite ore

This article focuses on the development of phase transformation and morphology of low-grade pyrolusite during carbothermal reduction using microwave heating. The XRD, SEM and EDS results show that selective carbothermal reduction of Mn_xO_y and Fe_xO_y in pyrolusite is easy to realize with microwave heating, which can reduce MnO₂ to MnO, and Fe₂O₃ to Fe₃O₄, rather than FeO. It was also observed that the phases of Mn₂O₃, Mn₃O₄ and MnO appear at 300?°C, 450?°C and 500?°C, respectively. The MnO phase, formed by the accumulation of MnO sphere particle with a diameter of 266.75–420.05?nm, is loose and porous. At a temperature of 750?°C, the Mn₂SiO₄ layer of about 316?nm in thickness, tightly wrapping SiO₂ particle is generated at the interface between MnO and SiO₂ embedded with MnO. Above 650?°C, Fe₂O₃ in pyrolusite can be transformed into a very dense Fe₃O₄ phase.     

Long-Term Transport Study of Bioartificial Tubule Devices in the Development of a Bioartificial Kidney

Introduction: A bioartificial kidney, which consists of a continuous hemofilter and a bioartificial tubule device using proximal tubular epithelial cells (LLC‐PK₁), is desired to develop for preventing long‐term complications in hemodialysis patients. A bioartificial tubule device should function for a long duration in terms of the simplicity and the economy. Continuous hemofiltration with 10 L/day of filtrate could maintain plasma urea, creatinine and β₂‐microglobulin in patients at low levels compared to those in standard hemodialysis patients. Methods: 6 bioartificial tubule devices, in which LLC‐PK₁ cells were grown on the inner surfaces of hollow fiber capillaries (membrane area: 0.4 m², 1600 fibers), were used to evaluate the transport ability of H₂O, glucose and Na⁺, and leak rates of urea and creatinine for 2 weeks when the medium containing 50 mg/dL of urea and 5.0 mg/dL of creatinine was perfused inside of the cell‐attached membranes and another medium containing 2.5 g/dL of albumin was perfused outside of the membranes. Scanning electron micrograph of cross‐sectional findings of the hollow fibers was taken at 6, 10, and 14 days after formation of confluence. Results: By conversion into 1 m² of membrane area, transport of H₂O, glucose, and Na⁺ was 6266 ± 995 mL/day, 22832 ± 7240 mg/day, and 941.3 ± 180 mEq/day, respectively at 6 days after confluence. Leak rates of urea and creatinine across the cell‐attached membranes were 22 ± 6.1% and 19.2 ± 4.9 with albumin addition, whereas 13.1 ± 1.9% and 12.2 ± 1.6 without albumin addition. Transport capacity of these components and the leak rates had continued for 10–13 days, and decreased thereafter because of the formation of the multilayers. Bioartificial tubule devices with membrane area 1.0 m² can reach the targeted amounts of H₂O, glucose, and Na⁺ transports when 6 L of 10 L/day of hemofiltrate has to be regenerated, substituting 4 L with meal and drinks.     

Influence of graphene oxide sheets on the pore structure and filtration performance of a novel graphene oxide/silica/polyacrylonitrile mixed matrix membrane

The novel graphene oxide (GO)/silica (SiO₂)/polyacrylonitrile (PAN) mixed matrix membranes (MMMs) with high filtration flux and excellent antifouling performance were designed and fabricated in situ by the method of non-solvent induced phase separation (NIPS) from the precursor of PAN hybridized with GO, tetraethoxysilane and 3-aminopropyltriethoxysilane. The influences of GO sheets on the pore and chemical structure, hydrophilic nature and filtration performance of derived GO/SiO₂/PAN MMMs were investigated by the scanning electron microscopy, field emission scanning electron microscopy, atomic force microscopy, energy-dispersive X-ray, Fourier transform infrared spectrometer, pure water contact angles and filtration performance. Results indicated that in situ incorporation of GO sheets and SiO₂ molecules into PAN matrix via NIPS reconstructs the porous structure of derived GO/SiO₂/PAN MMMs with the upright finger-like holes, porous bottom, thinner top layer and high porosity. The spontaneous surface migration or segregation of hydrophilic GO sheets and SiO₂ molecules as well as their synergistic interaction occurred during NIPS greatly ameliorate the top surface structure and property of derived membranes with smoother surface, uniform pore structure and good hydrophilicity. The derived GO/SiO₂/PAN MMMs exhibit a high water filtration flux of 387 L m^?2 h^?1 with the bull serum albumin rejection rate up to 99% and significant enhancement of antifouling performance.     

Pb/S/1,2-ethanedithiol composite thin films for efficient solid-state quantum-dot sensitized TiO<Subscript>2</Subscript> nanorod array solar cells

The Pb/S/1,2-ethanedithiol composite thin films were successfully deposited on TiO₂ nanorod arrays by spin-coating step-by-step 5 mmol dm^?3 Pb(NO₃)₂, Na₂S and 1% 1,2-ethanedithiol solution and their chemical compositions can be easily adjusted by changing the concentration of Na₂S solution from 5 to 3.5 mmol dm^?3 and 2 mmol dm^?3. The average crystal sizes of Pb/S/1,2-ethanedithiol quantum-dots decreased from 7.9 to 7.1 nm and 6.5 nm with the decrease of the concentration of Na₂S solution and the chemical bonding of Pb²⁺ and S in EDT was chelation of the penta-heterocycle in Pb/S/1,2-ethanedithiol composite thin films. All solid-state Pb/S/1,2-ethanedithiol composite thin film sensitized TiO₂ nanorod array solar cells using 5, 3.5, 2 mmol dm^?3 Na₂S solution exhibited the photoelectric conversion efficiency of 2.68, 3.41 and 4.51% under the illumination of simulated AM 1.5 sunlight (100 mA cm^?2).     

Cheaper membrane materials for microalgae dewatering

Among different strategies to reduce costs in microalgae dewatering process via cross-flow filtration, the one related to membrane material was investigated in order to be decreased. Several materials were tested, starting with the ones commonly used in membrane technology [ceramic, polysulfone (PSf) and polyacrylonitrile (PAN)] to the ones generally employed in packaging industry [acrylonitrile butadiene styrene (ABS), glycol-modified polyethylene terephthalate (PETG) and polylactic acid (PLA)], the latter being considerably cheaper. Experiments carried out showed promising results in terms of permeabilities for PSf–Pluronic^® F127 blended membranes and PAN membranes (11 ± 1 L/h/m²/bar and 22 ± 1 L/h/m²/bar, respectively, instead of 2 ± 2 L/h/m²/bar of PSf membranes), but with high related costs. PLA membranes showed good mechanical properties, biodegradability and price, but low permeability values (5 ± 1 L/h/m²/bar). PETG membranes showed attractive results in terms of costs and permeability, but poor mechanical properties. The polymer that offered the best results was the ABS that reached membrane permeabilities of 19 ± 1 L/h/m²/bar, maintaining good mechanical properties while filtering the microalgae Phaeodactylum tricornutum Bohlin. Thus, a novel functionality was found for these not so common polymers in microalgae dewatering. This indicates that use of these materials could also be considered in other aqueous micro/ultrafiltration applications. In addition, the biodegradable PLA polymer introduces a new concept of cheap and environmental friendly membrane in this application.     

MnO nanorods on graphene as an anode material for high capacity lithium ion batteries

The MnO/graphene hybrid nanocomposites were prepared by an in situ reduction method. The MnO₂ nanorods were attached on the graphene oxides (GOs) to form the MnO₂/GO nanocomposites, which were reduced to the MnO/graphene hybrid under argon atmosphere. As the anode material for the lithium ion batteries, the MnO/graphene electrodes delivered a high initial charge capacity up to 747 mAh g^?1 and a stable capacity of 705.8 mAh g^?1 after 100 cycles, which is much superior to pure MnO with initial charge capacity of 456 mAh g^?1 and the stable capacity of 95.6 mAh g^?1 after 100 cycles. The scanning electron microscope images of the MnO/graphene hybrid nanocomposites after cycling demonstrated that the graphene could prevent the MnO from aggregating during the charge/discharge process.     

Fabrication and characterization of microencapsulated PA with SiO<Subscript>2</Subscript> shell through sol–gel synthesis via sodium silicate precursor

In the present study, the microencapsulated phase change material with palmitic acid as core and inorganic SiO₂ shell was successfully fabricated by a sol–gel method in alkaline medium via sodium silicate precursor. The chemical compositions, crystalloid phase, microstructure and morphology of PA@SiO₂ microcapsule were studied by Fourier transform infrared spectroscopy, X-ray diffractometer, scanning electron microscopy and transmission electron microscopy. Differential scanning calorimetry and thermogravimetric analysis were used to determine the thermal properties and thermal stability of microcapsules, respectively. According to the XRD and FT-IR results, all the characteristic peaks of PA and SiO₂ were observed and there is no chemical reaction between them. Scanning electron microscopy images indicated that the microcapsule synthesized in pH 11 had a perfect spherical shape with smooth surfaces compared with other samples, and transmission electron microscopy images confirm that the PA have been well encapsulated by SiO₂. Differential scanning calorimetry analysis showed that the microcapsules indicated similar phase change behaviors as those of pristine PA, which melt at 67.2?°C with a latent heat of 111.2 J/g and freezing at 56.5?°C with a latent heat of 103.2 J/g. TGA analysis indicated that the thermal stability of the PA was also improved due to the protection of SiO₂ shell toward the encapsulated PA.     

The Degradation Behavior of SiC<Subscript>f</Subscript>/SiO<Subscript>2</Subscript> Composites in High-Temperature Environment

SiC_f/SiO₂ composites had been fabricated efficiently by Sol-Gel method. The oxidation behavior, thermal shock property and ablation behavior of SiC_f/SiO₂ composites was investigated. SiC_f/SiO₂ composites showed higher oxidation resistance in oxidation atmosphere, the flexural strength retention ratio was larger than 90.00%. After 1300 °C thermal shock, the mass retention ratio was 97.00%, and the flexural strength retention ratio was 92.60%, while after 1500 °C thermal shock, the mass retention ratio was 95.37%, and the flexural strength retention ratio was 83.34%. After 15 s ablation, the mass loss rate was 0.049 g/s and recession loss rate was 0.067 mm/s. The SiO₂ matrix was melted in priority and becomes loosen and porous. With the ablation going on, the oxides were washed away by the shearing action of the oxyacetylene flame. The evaporation of SiO₂ took away large amount of heat, which is also beneficial to the protection for SiC_f/SiO₂ composites.     

Amino-functionalized Fe3O4/SiO2 magnetic submicron composites and In3+ ion adsorption properties

Five kinds of amino-functionalized (polyaniline, poly(1,2-diaminobenzene), poly(1,3-diaminobenzene), poly(diphenylamine), and poly(o-toluidine)) Fe₃O₄/SiO₂ submicron composites (SCs) were prepared. The SEM and TEM results showed that these SCs possessed a sphere-like core/shell structure with an average diameter of ~500 nm. The XRD results indicated good crystallinity of Fe₃O₄ core, the amorphous SiO₂, and amino-functionalized shells. The XPS results confirmed that amino groups were plentiful rich outside the surface of these SCs which acted as the effective groups for adsorbing the metal ions. These SCs showed a good thermal stability at 20–250 °C. The high saturation magnetization of 60–70 emu/g is better than other similar reports. In³⁺ adsorption coefficients from aqueous solution by these SCs were higher than 10⁶ mL/g, indicating the higher selectivity and affinity to In³⁺ compared with Cd²⁺ and Hg²⁺ ions. In addition, these SCs could be magnetically reclaimed within 30 s and regenerated with acid after adsorption. The adsorption capabilities only decreased by 6 % after five cycles. The present work indicates that the amino-functionalized Fe₃O₄/SiO₂ SCs are promising for removal of In³⁺ ions in field application.     

A novel route for the preparation of CoCr<Subscript>2</Subscript>O<Subscript>4</Subscript>/SiO<Subscript>2</Subscript> nanocomposite starting from Co(II)–Cr(III) carboxylate complex combinations

This study reports the preparation and characterization of the spinel CoCr₂O₄. In order to obtain 20% CoCr₂O₄/80% SiO₂ and 50% CoCr₂O₄/50% SiO₂ (mol%) nanocomposites, we have used a versatile pathway based on the thermal decomposition of some particular precursors, Co(II) and Co(III) carboxylate-type complex combinations, inside the SiO₂ matrix. The ligands of these coordination compounds result in the redox reaction between Co(II) and Cr(III) nitrates and 1,3-propylene glycol by heating at 150 °C of the gels (tetraethylorthosilicate–metal nitrates–1,3-propylene glycol). The as-obtained precursors, embedded in silica gels, were characterized by FT-IR spectrometry and thermal analysis. Both precursors decompose up to 350 °C, leading to the corresponding metal oxides inside the silica matrix. X-ray diffraction of the powders annealed at different temperatures has evidenced the formation of CoCr₂O₄ starting with 400 °C for 20% CoCr₂O₄/SiO₂ and 300 °C for 50% CoCr₂O₄/SiO₂. This behaviour can be explained by the fact that, by thermal decomposition of the chromium carboxylates, a nonstoichiometric chromium oxide Cr₂O_3+x is formed. At ~ 400 °C, Cr₂O_3+x turns to α-Cr₂O₃, which interacts with CoO leading to cobalt chromite nuclei inside the pores of the silica matrix. CoCr₂O₄ has been obtained as nanocrystallites homogenously dispersed within the silica matrix as resulted from XRD, TEM and EDX mapping, with mean particle size in the range 5–20 nm.     

Reaction mechanisms,resultant microstructures and tensile properties of Al-based composites fabricated in situ from Al-SiO2-Mg system

Reaction mechanisms, microstructures and tensile properties of the aluminum matrix composites made from Al-SiO₂-Mg system were investigated. When the temperature increased from room temperature to around 761 K, Mg dissolved into Al to form Mg-Al alloy. As the temperature increased to about 850 K, the remaining Mg reacted with SiO₂ to form MgO, Mg₂Si and Si as expressed in step reaction I: 6Mg + 2SiO₂ → 4MgO + Mg₂Si + Si. Finally, with a further increase in temperature, the remaining SiO₂ reacted with Al to produce Al₂O₃ and Si, while MgO reacted with Al₂O₃ to form MgAl₂O₄ as expressed in step reaction II: 4Al + 3SiO₂ + 2MgO → 2MgAl₂O₄ + 3Si. The Si also dissolved into matrix Al to form Al-Si alloy. Accordingly, its reaction process consisted of two steps and their apparent activation energies were 218 kJ/mol and 192 kJ/mol, respectively. As compared to the composites prepared by Al-SiO₂ system, its density increased from 2.4 to 2.6 g/cm³, and its tensile strength and elongation increased from 165 MPa and 3.95% to 187 MPa and 7.18%, respectively.     

Active Soldering of ZnS–SiO2 Sputtering Targets to Copper Backing Plates Using an Sn56Bi4Ti(Ce,Ga) Filler

ZnS–SiO₂ targets have been directly soldered to copper backing plates at 180°C in air using an Sn56Bi4Ti(Ce, Ga) filler. The affinity of cerium to oxygen protects titanium from oxidation, allowing titanium to react with ZnS–SiO₂ sputtering target. The shear strengths are 1.7, 8.7, and 1.3 MPa for ZnS–SiO₂/ZnS–SiO₂, copper/copper and ZnS–SiO₂/copper joints, respectively. EPMA elemental mapping shows that aging test at 120° for 100 hours enhanced the segregation of titanium at the ZnS–SiO₂/solder interfaces. The shear strength of ZnS–SiO₂/copper joint after aging test is 1.3 MPa that shows no trace of degradation compared to the initial quality of the samples.     

Biocompatible hydrophilic brushite coatings on AZX310 and AM50 alloys for orthopaedic implants

Dicalcium phosphate dihydrate (DCPD) brushite coating with flake like crystal structure for the protection of AZX310 and AM50 magnesium (Mg) alloys was prepared through chemical deposition treatment. Chemical deposition treatment was employed using Ca(NO₃)₂·4H₂O and KH₂PO₄ along with subsequent heat treatment. The morphological results revealed that the brushite coating with dense and uniform structures was successfully deposited on the surface of AZX310 and AM50 alloys. The X-ray diffraction (XRD) patterns and Attenuated total reflectance infrared (ATR-IR) spectrum also revealed the confirmation of DCPD layer formation. Hydrophilic nature of the DCPD coatings was confirmed by Contact angle (CA) measurements. Moreover, electrochemical immersion and in vitro studies were evaluated to measure the corrosion performance and biocompatibility performance. The deposition of DCPD coating for HTI AM50 enables a tenfold increase in the corrosion resistance compared with AZX310. Hence the ability to offer such significant improvement in corrosion resistance for HTI AM50 was coupled with more bioactive nature of the DCPD coating is a viable approach for the development of Mg-based degradable implant materials.

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Proton conductive membranes based on silicotungstic acid/silica and polybenzimidazole

Membranes formed by polybenzimidazole and silicotungstic acid supported on silica have been prepared. The membranes were characterized in order to evaluate their proton conduction, mechanical stability and structural characteristics. Silica produced a beneficial effect on proton conduction of the membranes. The membranes with 50 wt.% of SiWA–SiO₂/PBI was mechanically stable and gave proton conductivity of 1.2×10⁻³ S cm⁻¹ at 160°C and 100% relative humidity. All the materials prepared had amorphous structure.     

The influence of hydrothermal synthesis conditions on gyrolite texture and specific surface area

Influence of hydrothermal synthesis conditions on the gyrolite specific surface area, dominant pore size and their differential distribution by the radius were determined. The synthesis of gyrolite has been carried out in unstirred suspensions within 32, 48, 72, 120, 168 h at 200°C temperature from a stoichiometric composition (the molar ratio of CaO/SiO₂ was equal to 0.66 where water/solid ratio of the suspension was equal to 10.0) of the initial CaO and SiO₂·nH₂O mixture. It was found that the structure of gyrolite and the shape of dominated pores (from pores between parallel plates to cylindrical pores) changes prolonging the duration of hydrothermal synthesis. The stable gyrolite crystal lattice was formed only after 120 h of isothermal curing. Its specific surface area S _BET = 38.28 m²/g, the radius of dominant plate pores r _p = 30–40 Å, the cumulative pore volume ΣV _p = 0.08 cm³/g. It was determined that the pores with 4.0–5.0 nm radius were dominated in gyrolite structure after 168 h of synthesis. It was estimated that the ion exchange between gyrolite with less orderly structure in Zn(NO₃)₂ + NH₄OH alkaline solution ( ${c_{{{\text{Zn}}^{2+}}}}$ —0.3 g/dm³) proceeds more faster and effectively.     

Synthesis and structural, optical and electrical properties of TiO2/SiO2 nanocomposites

Sole components of titania (TiO₂), silica (SiO₂) nanoparticles, and binary TiO₂–SiO₂ nanocomposites with various molar ratios of silica contents were prepared by modified sol–gel method. The samples were calcined at 500 °C for 5 h and characterized by X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), UV–Vis spectroscopy, Brunauett–Emmett–Teller (BET), and photoconductivity. The crystallite size for TiO₂/SiO₂ nanocomposites was calculated using Scherrer’s formula and found to be 5 nm for TiO₂ nanoparticles. The binary oxide shows the anatase type of TiO₂ at the mole ratio up to 80 mol% of TiO₂ added. The band gap for as-synthesized nanocomposites was calculated and it was found that the band gap decreases with increase of SiO₂ content and then decreases with excess SiO₂ content. FTIR confirms that both TiO₂ and SiO₂ phases have been formed. The BET surface area for TiO₂/SiO₂ nanocomposite is found to be 303 m²/g, and pore size distribution has an average pore diameter about 10 nm for 40 mol% of TiO₂ added. It also confirms the absence of macropores and the presence of micro and mesopores. The field-dependent dark and photoconductivity studies reveal that the dark and photocurrent increase linearly with applied field confirming the ohmic nature of the electric contacts. The dark and photocurrent increase slightly with increase of SiO₂ content and decrease with excess amount of SiO₂.