CN102103097B - Method for researching standard molar enthalpy of formation of platy nanometer ZnO - Google Patents

Abstract

The invention provides a novel idea for searching a relationship between the standard molar formation enthalpy of platy nanometer ZnO and the standard molar formation enthalpy of blocky ZnO by using the known standard molar formation enthalpy of the blocky ZnO as a reference standard to obtain the standard molar formation enthalpy of the platy nanometer ZnO for the first time. Based on the novel idea, the invention further provides a novel method for obtaining the standard molar formation enthalpy of the platy nanometer ZnO through the same chemical reaction of the platy nanometer ZnO and the blocky ZnO under the same condition respectively. The standard molar formation enthalpy of the platy nanometer ZnO of -286.32kJ/mol under the conditions of 298.15K and p<theta> is obtained by a micro calorimeter with high accuracy and sensitivity according to a thermodynamic potential function method.

Description

A Method for Studying Standard Molar Formation Enthalpy of Flake Nano ZnO

technical field

The present invention relates to a research on the standard molar enthalpy of formation of flake nano-ZnO, in particular to a method of using the known standard molar enthalpy of formation of bulk ZnO as a reference standard to seek the relationship between the standard molar enthalpy of formation of flake nano-ZnO and bulk ZnO , so as to obtain the standard molar enthalpy of formation of flake nano-ZnO.

Background technique

The entropy, enthalpy, Gibbs free energy and other prescribed thermodynamic functions of nanomaterials have important scientific significance and application value, and are functions of scale and shape. How to obtain the specified thermodynamic function values of nanomaterials through experiments, explore the scale, orientation (morphology) relationship and evolution law of nanometer thermodynamic functions, and establish basic thermodynamic data standards for nanomaterials with different sizes and orientations (morphologies), is the "nano An important topic in the study of thermodynamics of materials. The current research on the thermodynamic properties of nanomaterials is very lacking, especially the research on the entropy, enthalpy, Gibbs free energy and other prescribed thermodynamic function values of nanomaterials.

Yue Danting et al. measured the low-temperature heat capacity of a variety of different nanomaterials (such as nano-zinc oxide, nano-iron, and nano-aluminum) by the same method. According to the relationship between the heat capacity and the thermodynamic function, the standard state 298.15K was used as the benchmark. The entropy, enthalpy, and Gibbs free energy of nanomaterials, its representative literature such as [Yue Danting, Tan Zhicheng, Dong Lina, Sun Lixian, Zhang Tao. Acta Physicochemical Sinica 2005, 21: 446-449.]; Lai Weipeng et al. combined with theoretical models, Various standard enthalpy and standard entropy of nano-diamonds with different particle sizes obtained by quantum chemical method obtained the standard molar enthalpy of formation data of a variety of nano-phosphate compounds prepared by solid-state reaction through the reaction heat of the nano-reaction system using a microcalorimeter, and its representative literature is [a) Yuan AQ, Liao S, Tong Z F , Wu J, Huang ZY. Mater. Lett.2006, 60:2110-2114.b) Yuan AQ, Wu J, Bai LJ, Huang ZY, Wu K, Liao S, Tong ZF. Mater. Res. Bull.2008, 43:1339-1345.c) Yuan AQ, Wu J, Bai LJ, Ma SM, Huang ZY, Tong ZF.J.Chem.Eng.Data 2008, 53:1066-1070.].

The problem with the above methods is that the entropy, enthalpy, and Gibbs free energy of nanomaterials obtained by measuring the low-temperature heat capacity are based on the standard state of 298.15K instead of 0K, so it does not solve the problem of nanomaterials in essence. The value of the specified thermodynamic function; the establishment and application of the theoretical model is only suitable for nanomaterials that meet specific conditions, so the scope of application is narrow; the standard molar enthalpy of formation of nanomaterials must be known through the reaction heat of the nanometer reaction system. The standard molar enthalpy of formation of each substance is also not applicable to liquid phase reactions. At present, the idea and specific method of obtaining the standard molar enthalpy of formation of nanomaterials by using the known standard molar enthalpy of formation of bulk materials as a reference standard to seek the relationship between the standard molar enthalpy of formation of nanomaterials and corresponding bulk materials has not been reported.

Contents of the invention

The purpose of the present invention is to provide a new idea and a new method for obtaining the standard molar enthalpy of formation of nanomaterials in order to overcome the defects and deficiencies in the above-mentioned existing methods. The new idea has been verified by a specific new method, supporting the new ideas.

The purpose of the present invention can be achieved through the following technical solutions: a new idea and new method for studying the standard molar enthalpy of formation of sheet-like nanometer ZnO, characterized in that the new idea is to use the known block ZnO standard molar enthalpy of formation as a reference standard , to seek the relationship between the standard molar enthalpy of formation of flake nano-ZnO and bulk ZnO, so as to obtain the standard molar enthalpy of formation of flake nano-ZnO. The new method is specifically established based on this new idea. Specifically, under the same conditions, the same chemical reactions occur in the flake nano-ZnO and bulk ZnO respectively. According to the thermodynamic potential function method, the standard molar ratio of flake nano-ZnO and bulk ZnO is obtained. The relationship between the enthalpy of formation, and finally a new method to obtain the standard molar enthalpy of formation of flake nano-ZnO. The feasibility of the new method demonstrates the correctness of the new idea. Specific steps are as follows:

1) At 298.15K and p ^θ , react flake nano-ZnO and block ZnO with excess hydrochloric acid of the same concentration respectively, and measure the reaction enthalpy change of zinc oxide nano-reaction system and block reaction system respectively by microcalorimeter ;

2), after the reaction is complete, use inductively coupled plasma (abbreviation ICP) to measure the concentration of zinc ions in the ZnO nanometer reaction system and the bulk reaction system, to determine the amount of zinc oxide reaction in the two systems, and obtain the two systems. Molar Enthalpy Change of Reaction

3), according to the thermodynamic potential function method, the relationship between the ZnO nanometer reaction system and the bulk reaction system is established, and the relationship between the standard molar formation enthalpy of sheet-like nano-ZnO and bulk ZnO is obtained as follows:

${\mathrm{<span\; class="notranslate">\; \&Delta;</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; A</span>}}^{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; ZnO</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; bulk</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; A</span>}}^{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; ZnO</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; nano</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; nano</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; bulk</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ;</span>$

4), through the known standard molar enthalpy of formation of bulk ZnO, combined with the relationship between the standard molar enthalpy of formation of flake nano ZnO and bulk ZnO in step 3, the standard molar enthalpy of formation of flake nano ZnO is obtained.

Compared with the prior art, the present invention has the following characteristics:

1. The new idea in the present invention is based on the standard molar enthalpy of formation of the bulk material, because the standard molar enthalpy of formation of the bulk material can be obtained by checking the manual.

2. The new idea of the present invention is to seek the relationship between the standard molar enthalpy of formation of flake nano-ZnO and bulk ZnO as the main line.

3. The new method in the present invention cleverly links the standard molar enthalpy of formation of flake nano-ZnO and bulk ZnO.

4. The new method in the present invention has wide applicability, simple operation, accurate and quick data acquisition.

Description of drawings

Fig. 1 implements the schematic diagram of the principle of the thermodynamic potential function method of the standard molar enthalpy of formation of connecting flake nanometer ZnO and bulk ZnO for the present invention;

Fig. 2 is the SEM picture of the flaky nano-ZnO that reacts with hydrochloric acid in the embodiment of the present invention 1

Detailed ways

The present invention will be further described below in conjunction with specific examples. The description of the examples is only to facilitate the understanding of the present invention, but not to limit the protection of the present invention.

Example 1

1. At 298.15K and p ^θ , a certain amount of flaky nano-ZnO was reacted with excess hydrochloric acid with a concentration of 0.26mol/L and a volume of 1.5mL in a microcalorimeter, and the measured reaction enthalpy became -0.28028J , the reaction solution was fixed to volume with a 10mL colorimetric tube, and the zinc ion concentration was measured by ICP as 2.0322 mg/L, and thus the molar reaction enthalpy of the nanometer reaction system became -901.71kJ/mol;

2. At 298.15K and p ^θ , a certain amount of bulk ZnO was reacted with excess hydrochloric acid with a concentration of 0.26mol/L and a volume of 1.5mL in a microcalorimeter, and the measured reaction enthalpy became -0.21925J, The reaction solution was fixed to volume with a 10mL colorimetric tube, and the concentration of zinc ions measured by ICP was 1.7070mg/L, thus the molar reaction enthalpy of the block reaction system was changed to -839.75kJ/mol;

3. According to the thermodynamic potential function method, the relationship between the ZnO nano-reaction system and the bulk reaction system is established, and the relationship between the standard molar formation enthalpy of sheet-like nano-ZnO and bulk ZnO is obtained as follows:

${\mathrm{<span\; class="notranslate">\; \&Delta;</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; A</span>}}^{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; ZnO</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; bulk</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; A</span>}}^{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; ZnO</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; nano</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; nano</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; bulk</span>}<span\; class="notranslate">\; )</span>$

最终可得片状纳米ZnO的标准摩尔生成焓

Standard Molar Enthalpy of Formation of Bulk ZnO at 298.15K and p ^θ

The standard molar enthalpy of formation of the finally available flake nano-ZnO

Claims (2)

1. A method of researching flake nano ZnO standard molar enthalpy of formation, the concrete steps are: 1) At 298.15K and p ^θ , react flake nano-ZnO and block ZnO with excess hydrochloric acid of the same concentration respectively, and measure the reaction enthalpy change of zinc oxide nano-reaction system and block reaction system respectively by microcalorimeter ; 2), after the reaction is complete, use inductively coupled plasma (abbreviation ICP) to measure the concentration of zinc ions in the ZnO nanometer reaction system and the bulk reaction system, to determine the amount of zinc oxide reaction in the two systems, and obtain the two systems. Molar Enthalpy Change of Reaction

3), according to the thermodynamic potential function method, the connection between the ZnO nanometer reaction system and the bulk reaction system is established, and the relationship between the standard molar formation enthalpy of sheet-like nano-ZnO and bulk ZnO is obtained as:

4), through the known standard molar enthalpy of formation of bulk ZnO, combined with the relationship between the standard molar enthalpy of formation of flake nano ZnO and bulk ZnO in step 3, the standard molar enthalpy of formation of flake nano ZnO is obtained. 2. the method for obtaining the standard molar enthalpy of formation of flaky nano ZnO according to claim 1 is characterized in that: same chemical reaction takes place under identical conditions with flaky nano ZnO and block ZnO, utilizes thermodynamic potential function method to seek The relationship between the standard molar enthalpy of formation of nano ZnO and bulk ZnO, thereby obtaining the method for the standard molar enthalpy of formation of flake nano ZnO. the

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