| Indoor environmental humidity not only affects the comfort of the human body,but also has a vital impact on the propagation of indoor microorganisms,the release of harmful gases and the preservation of objects.The traditional approaches to adjust the indoor humidity are using air conditioner,dehumidifier and humidifier,which consume energy,take up space and generate noise.In order to avoid these deficiencies,developing a humidity control material with the advantages of no energy consumption and self-adaptive adjustment,which has become a hot research direction for humidity controlling.The inorganic silicon-based mesoporous materials have the advantages of rich pore structure,large moisture storage capacity,easy regeneration,good thermal stability and non-toxicity,and are considered as an ideal humidity control material.However,there are many problems in the current preparation methods of inorganic silicon-based mesoporous materials,including the complex process,long cycle and high cost.In addition,the moisture regulation mechanism of the inorganic silicon-based mesoporous materials is unclear at now.These problems have led to the failure of inorganic silicon-based mesoporous materials to be widely used in indoor humidity control.Therefore,it is a great scientific significance and economic value to study the moisture regulation mechanism and low-cost preparation of inorganic silicon-based mesoporous materials.In this dissertation,a template approach was employed to prepare inorganic silicon-based mesoporous materials with various pore structure characteristics.The main influencing factors and moisture regulation mechanism of the prepared inorganic silicon-based mesoporous materials were shown by investigating the effect of the pore structure characteristics of the materials on the humidity control performance,which provides theoretical and application guidance for preparing inorganic silicon-based mesoporous materials using a non-template approach.This dissertation presented the preparation of mesoporous humidity-controlling materials based on inorganic silicon directly from abundant and cheap volcanic ash using the non-template approach via an acid-base etching process and successfully applied inorganic silicon-based mesoporous materials to fabricate humidity-controlling ceramic tiles.Finally,a moisture buffer coefficient-evaluation approach was proposed and an experimental model was established to evaluate the ability of the ceramic tile to adjust indoor humidity in an actual environment.The main research content and findings are listed below.(1)Using poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)triblock copolymer,ethyl orthosilicate and 1,3,5-trimethylbenzene as the main materials,a spherical silica mesoporous material with narrow aperture distribution was prepared using a template approach.By controlling the hydrothermal reaction temperature and time,the average pore diameter and pore volume of the spherical silica mesoporous material can be controlled in the ranges of 0.7-19.1 nm and 0.19-0.54 cm~3/g,respectively.The moisture absorption and dehumidification rates of the inorganic silica-based mesoporous materials in the specified humidity range are closely related to the pore volume size during capillary condensation.1)The moisture content of the mesoporous materials is proportional to the total pore volume of the mesoporous materials with a pore size of≤1.8 nm at 30%relative humidity.2)The hygroscopicity of the prepared inorganic silicon-based mesoporous materials at 30%–50%relative humidity is proportional to the total pore volume of the holes with pore sizes of 1.8–3.0 nm.3)The hygroscopicity of the prepared inorganic silicon-based mesoporous materials at50%–70%relative humidity is proportional to the total pore volume of the holes with pore sizes of 3.0–5.9 nm.4)The hygroscopicity of the prepared silica mesoporous materials at 70%–-95%relative humidity is proportional to the total pore volume of the material with pore sizes of 5.9–41.1 nm.5)The moisture content at 95%relative humidity is directly proportional to holes’total volume with a pore size of≤41.1 nm.(2)Using volcanic ash as the main raw material,the silica-based mesoporous materials with an average pore size range of 5.0–18.6 nm and a pore volume range of 0.33–1.32 cm~3/g were prepared with a non-template approach by controlling the concentration of acid and alkali etching solution and the etching temperature.Increasing the concentration of alkaline etching solution was beneficial to the in-situ dissolution of quartz and cristobalite and forming of nanopores in the process of alkaline etching.The increasing etching temperature can enhance the transformation of lamellar chlorite to partial trioctahedral zeolite and reduce the pore structure formed by accumulating lamellar structure in the product.A response surface approach was employed to further optimise the process conditions of non-template preparation of inorganic silica-based mesoporous humidity-controlling materials.The optimal preparation conditions were determined as follows:an alkali etching solution concentration of 8 mol/L,alkali etching temperature of 100°C,acid etching solution concentration of 8 mol/L and acid etching temperature of 140°C.Under these conditions,silica-based mesoporous materials were prepared with hygroscopicity of 87.9%at 50%–95%relative humidity,the specific surface area of 420.7 m~2/g,pore volume of 1.31 cm~3/g and average pore size of 11.7 nm.(3)Using volcanic ash,kalialbite and inorganic silica mesoporous materials as the main raw materials,adopting the preparation technology of traditional ceramic tile,by controlling the ratio of raw materials and preparation technology,ceramic tiles average flexural strength is2.6–20.4 MPa,and the moisture absorption capacity is 51.2–448.5 g/m~2.The effects of the addition amount of inorganic silica-based mesoporous materials,moisture content of granulation,glaze’s coating amount and firing temperature on the properties of humidity-controlling ceramic tiles were investigated.Studies have found that under the condition of the same preparation technology,with the increase of inorganic silicon-based mesoporous materials,the absorption and desorption moisture content for the prepared ceramic tile increases,the flexural strength rises and then fall.When the inorganic silicon-based mesoporous materials adding amount is≤2%,the inorganic silicon-based mesoporous materials can react with the calcium in the formula components,formed in the billet body roll of foil sheet hydrated calcium silicate phase.The interspersed and stacking of these foil sheets can enhance the ceramic tile body’s strength.The excessive introduction of inorganic silica-based mesoporous materials will reduce the green body’s density when the addition amount of inorganic silica-based mesoporous materials is more than 2%,decreasing green body strength.The addition of 2%inorganic silica-based mesoporous materials can increase the ceramic tile’s flexural strength by 20%and the moisture absorption capacity by 2.7 times compared with the ceramic tile without inorganic silica-based mesoporous materials.On this basis,the mass ratio of the volcanic ash,kalialbite and inorganic silica-based mesoporous materials is 50:50:2.The pressed dry body was decorated with inkjet and fired at 700°C to prepare hygroscopic ceramic tiles with rich decorative effect under the conditions of 15%granulation moisture and 70 g/m~2 glaze spraying amount,with an average flexural strength of 15.2 MPa and moisture absorption capacity of 303g/m~2.The product’s flexural performance conforms to the standard requirements of GB/T 4100-2015 ceramic tile,and the moisture absorption and release capacity is 5 times the standard of JC/T 2082-2011 humidity control Function Interior Building Decoration Materials.(4)An experimental box and an artificial climate chamber were employed to simulate indoor and outdoor environments,respectively.By establishing an experimental model,a moisture buffer coefficient-evaluation approach was proposed to evaluate the applicability of hygroscopic materials in an actual environment.The absorption and desorption buffer coefficient under different working conditions(different intake air temperatures and humidities,different air change rates and humidity-controlling material contents)were obtained by estimating the change curve of humidity as a function of time when air was passed through the indoor environment at the same flow rate,temperature and humidity,before and after the hygroscopic material-based ceramic tiles were laid.The fitting equation of the moisture-absorption buffer coefficient and moisture-desorption buffer coefficient of the ceramic titles is obtained by fitting the moisture buffer coefficient under different working conditions.From the fitting equation of the moisture buffer coefficient,it can be concluded that ceramic tiles’humidity control effect in a building increase exponentially with the increase in the ratio of the room humidity control material to the indoor volume and the ratio of air change rates.On the premise of meeting the architectural design specifications,the indoor humidity can be reduced by 52%by paving 12 m~2 humidity-controlling ceramic tiles in a 12 m~2 bedroom when 23°C/95%relative humidity of air is passed into the room for 24 consecutive hours,and the humidity can be reduced by 39%when the 23°C/30%relative humidity of air is passed into the room for 24consecutive hours.Humidity self-regulating ceramic tiles have outstanding humidity control performance. |
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